Honestly, I am puzzled myself about why I dislike Hye Won. When I have more complaints about Kang In Ha than Hye Won!
So I rewatched her scenes again and you see, her very first conversation with Tae Oh in front of a coffee vending machine is actually a good one. Not too much not too little...
The only thing that directly bothered me may just be her speech style. So enlighten me politely please ?
Why did I dislike her?

well.

because maybe just as me you don't recognise what her deal is!!  Is she upto creating trouble b/w taeho&inha?! or is she only wanting to use inha for her personal benefits cause she knows his background?! Is she faking her fondness for taeho?! cause she is aware he is hard to read just the way she pretends she is,!! 

 she might find taeho as a person soon to become a potential trouble for her in the future cause these two are alike & Taeho is intellectual with brains. Which highlights the reason why she let inha kiss her & even resorted for moving in his house but previously she wasn't and even told straight away to taeho something like " if I move homes, these thugs might think I consider that lady my mom & I don't want that".   And i'm 100percent sure she wanted to look somewhat courageous & mysterious in Taeho's eyes. But this trick didn't work & now she was forced to think of plan B and that was inha! And it worked.  Cause if she were Honest with Taeho in regard to whatever she said she could've easily left but no she wanted to experiment with if he comes back & while he did yet fate had different plans and she chose inha/forced to choose inha !!. Yet again she is not honest!! i.e in that ending night scene on the street she goes like "we need to move ahead or else we'll regret it" (something like this). But 5 Mins Later,,, she is banging on Taeho's door. 

Also ! also! Also! Her shutting off Inha's confession by telling him(( infront of Taeho)) that she's too busy to date & meanwhile giving all her attention to Taeho ((infront of inha)) was the utmost biggest annoying gesture that totally made me go like " IS SHE OKAYYYY?!?!?;"

So moral of the story: this female lead PRETENDSSS & that's what annoys me about her character. inha is kinda naive he won't get her tricks but Taeho Ain't !! And that is why Taeho despite liking her doesn't let himself get wrapped around her finger, he must stay focused.

While I also believe if she were Actually Truly honest with him about her true nature and self he wouldn't have let her go & won her over.

Guess I like my pookie Hyijuu more so imma ship taeho with her though there are less chances of the ship sailing !!

[ I am half asleep hope my answer wasn't confusing & yes we don't necessarily need to like her but I am excited to read her character more ]

Aside from her Bad Acting. Her character is cliche, and badly written. 

 myulmangalltheway:
because maybe just as me you don't recognise what her deal is!!  Is she upto creating trouble b/w taeho&inha?! or is she only wanting to use inha for her personal benefits cause she knows his background?! Is she faking her fondness for taeho?! cause she is aware he is hard to read just the way she pretends she is,!! 

it's not up to the people who are watching but the makers who didn't put effort into presenting her character well. She had motives to do what she was doing but they didn't show it well. In 2nd epi, she gets ML's attention without doing anything, She just approaches his Best friend, and Tada gets the boy. Even tho he knows his friend likes her, even tho he sees them talking about him in the library, he puts all of his brains aside and goes for her. 

 Lily Jhonson:

Aside from her Bad Acting. Her character is cliche, and badly written. 

it's not up to the people who are watching but the makers who didn't put effort into presenting her character well. She had motives to do what she was doing but they didn't show it well. In 2nd epi, she gets ML's attention without doing anything, She just approaches his Best friend, and Tada gets the boy. Even tho he knows his friend likes her, even tho he sees them talking about him in the library, he puts all of his brains aside and goes for her. 

agree with what you said " she had motives to do what she was doing but they didn't show it well" and this is exactly what makes her a one dimensional character & given the scenario b/w the leads and tightness of the plot audience needs proofs and solid motivations that drives them & honestly i'm seeing nothing from her side apart from the mom thing which was too clichè as you also mentioned.

While i wanna mention Taeho  even though we have some backstory of his it doesn't feel like that I need more to understand what drives him like his acting is top-notch atleast for me.  KangInHa on the side i don't trust him, he is extremely friendly and lowkey psyco.

Her character is a representation of a gold digger, "in reality any chaeabols marry a nobody girl and her family awful and a unknown girl wants to climb social ladder" Chaebols marry within in their socioeconomic class. Aside from FL, story would great potential but ruined with bad writing and direction.

 Lily Jhonson:

Aside from her Bad Acting. Her character is cliche, and badly written. 

it's not up to the people who are watching but the makers who didn't put effort into presenting her character well. She had motives to do what she was doing but they didn't show it well. In 2nd epi, she gets ML's attention without doing anything, She just approaches his Best friend, and Tada gets the boy. Even tho he knows his friend likes her, even tho he sees them talking about him in the library, he puts all of his brains aside and goes for her. 

Couldn't agree more with you and myulmangalltheway and yall both can explain it with words better than I ever could hahaha. I know the FL is noob compared to her peers and all but  I don't get the hate on her. It's clear as day that her character sucks and even more experienced actors wouldn't be able to make it a likeable character without major changes.

The first ep and I wanted to gouge  my ears out with a ice pick.  The sound of her voice is giving the the hives.   I could go into the beyond terrible acting OMG is it BAD!!

The actor in the Tae Oh role always has the same expression on his face in his roles.    Even if he smiles or is happy he still has the look of someone that's about to eat  their last meal and about to be marched off to their death.

I have no problem with her character after watching 6 ep.  She is realistic character. I guess people didn’t like her because she is not cliche character where a girl sacrifice herself for love , she is not the type of honest FL. She is ambitious, persistant and smart, but at the same time she is not evil girl, who do everything for power, at least for now, we don’t know how she will change, I’m pretty sure she will change, In Ha will change her I guess but at the same time he will be disappointed on that changes.  She wants big and she doesn’t hide it from In Ha also. I would say that Tae Ho and Hye Won made bad choice because they were no ones those times.  They could study and make a good life together but that was not enough for both of them, so there is no one to blame.  That kiss is mess of course:))) but sh*t happens:)) if you did expect romance & bromance from this drama, oh pls no:))) don’t be naive, it will get worse when jealousy is mixed, can’t wait. Btw I don’t see a happy ending for anyone here. But somehow they will reach their goals, will they find happiness, I don’t think so. 

 Zhankarr:
She is realistic character. I guess people didn’t like her because she is not cliche character where a girl sacrifice herself for love , she is not the type of honest FL.

I don't agree with that, we don't like cliche characters FL's. It's just we have seen so many Kdramas with better acting and plot. That now we refuse the Kdrama if it's not as good as expected.  As for the acting, FL's acting sucks, no doubt about it.

Her character possessed the unlikeable trait of a beautiful woman. 

  1. She plays with men's hearts. string along guys and being indecisive who to pick and mess up "friendship" of MLs that the show got viewers emotionally invested in. (even if later reveal that she's also got played. It's still bad characteristic for anyone to do what she did.) 
  2. She wants money and power but is not getting them herself. She depends on Inha (who depends on Teaoh). she's doing the minimum work that can be giving to anyone else. If she's more savvy and pulls some strings of her own it'd make her more interesting. but as far as we know (EP6) she's basically doing what she's told. which makes her unlikeable to viewers.
  3. The writer fails to make viewers sympathize with her.  They don't give her scenes where we can understand or feel connected to as human beings. The scenes we get are not enough tbh.

I feel like any girl who takes on this role will need to have the aura that can turn shit into a rainbow. she needs to be a unicorn, to be so charismatic that people will blame the script instead of her acting.

but sadly, she isn't a unicorn.

Her acting is kinda lacking.  Bad writing is debateable. but when two MLs and the others are doing thier good job and nailing microexpressions, her inferiority is showing. Even in emotional scenes, her eyes just look wide open and only her moth moves. it looks unsettling.

I like her in normal scenes. She looks cold and mysterious. but her emotional scenes ruin it. 

That’s why I like her, because she is with fails and insecurities. And I like that she will become a turning point for 2 ML:)) why everyone expecting strong character with no faults)) she wants money and power, what’s the deal?! I really don’t see a problem with that. I would hate her if she would be a naive girl with no ambitions, it would be another cliche kdrama with sweet and naive girl.

 chickwifey:

The first ep and I wanted to gouge  my ears out with a ice pick.  The sound of her voice is giving the the hives.   I could go into the beyond terrible acting OMG is it BAD!!

The actor in the Tae Oh role always has the same expression on his face in his roles.    Even if he smiles or is happy he still has the look of someone that's about to eat  their last meal and about to be marched off to their death.

Have you seen him in Search WWW or When the weather is fine? 

 Zhankarr:
she is with fails and insecurities. And I like that she will become a turning point for 2 ML:)) why everyone expecting strong character with no faults)) she wants money and power, what’s the deal?! I really don’t see a problem with that. I would hate her if she would be a naive girl with no ambitions, it would be another cliche kdrama with sweet and naive girl.

Please watch some good kdrama with a strong female lead also, that's a very old and cliche plot (sweet and naive girl with the rich hire).  the problem is a lack of creativity from the writing team as well as the bad acting, the FL didn't have any charm to make the audience like her, she didn't have an FL vibe, even if she wanna be bad@ss and mysterious, she appears as a mean side character, not an FL.

 Okaybabe:
. She depends on Inha (who depends on Teaoh). she's doing the minimum work that can be giving to anyone else.

She is so effortless that we(audience) can't see her efforts in the plot. LOL!

 Okaybabe:
They don't give her scenes where we can understand or feel connected to as human beings.

Exactly my thoughts! even if, she is one being played by ML, her backstory is so cliche, not have enough motivation, audience like ambitious FL but she is just a mean girl. 

 Zhankarr:

That’s why I like her, because she is with fails and insecurities. And I like that she will become a turning point for 2 ML:)) why everyone expecting strong character with no faults)) she wants money and power, what’s the deal?! I really don’t see a problem with that. I would hate her if she would be a naive girl with no ambitions, it would be another cliche kdrama with sweet and naive girl.

Character-wise, she has this similar trope to Oh Soo Ah from Itaewon Class. Both were coming from not-so-fortunate backgrounds and chose to love themselves more rather than their romantic others. Which is plausible! But compared to Oh Soo Ah, Hye Won's character feels more plain and inferior.
When Oh Soo Ah has a full liveable and layered character (complex and presentable) supported by top-notch acting, even when we audience is invested in the main character and energetic FML, we can't brush her off right away. Oh Soo Ah was just as annoying as Hye Won but we understand where she came from and why she made such a decision (and as long as I remember, there's no such conversation that questioning Kwon Na Ra's acting). Meanwhile, there's a lack of consistency in Hye Won's character plus the actress failure to convince us with her emotional acting.

Oh Soo Ah even has a dialogue like "please be rich and save me!" Said to Park Sae Ro Yi, yet even from such a scene I feel the layer of her words. It half sounds like "be strong PSRY" and  "truly be strong and save me because I'm so tired"

See...
But after 6 episodes, I still failed to sympathise with Hye Won. Honestly, between Hye Won and Hee Ju's character, Hee Ju has more potential to be b*tch compared to Hye Won's. But Hee Ju's acting helped so much and was convincing.
Another thing, at the last dinner scene with the chairman ? she so foolishly confronts the old man with what confidence? It's so ridiculously funny to feel more meaning in Hee Ju's simple sarcastic 'bravo' to Hye Won's false bravery. She can't read the room ? She has nothing to put on the table, so it's understandable to be looked down upon, especially when your in-law-to-be has an abundance on their plate. The best course of action? Be humble! (It's the writer's mistake if the writer intended Hye Won to be a pivotal character). Be humble and move under their radar until you have enough power to do otherwise. Except if the writer intends to write her as a brainless gold digger.
For me, it's both the writer and the actress's failure. The writer clearly f*ck up with such a crappy and hurried structure. But they are blessed with many good actors and actresses, of course immediately her inferior acting is noticeable. Make me wonder Why?? Why did they cast her when it's one of few dramas with almost perfect casting? The chairman, the sons, that lady of the 'Kang' house, and even to their butler show such spectacular acting. So Why?? Not even once in 6 episodes she managed to convince me as audience with her acting.
That's my conclusion of why I ended up not favoring her characters ?