Does any one know the name of an Asian show of a poor girl
who is mistreated by her own sister? The girls do not know they are sisters. The poor girl is the secret daughter of a wealthy family and lives a poor life working in a mall. Her sister sabotages her work at the mall and in an office.  The poor girl may work designing things.  Also, there is a guy who both girls fall in love with.

I remember they work together at an office, but the girl is mistreated since she is poor. For example, others go to lunch and leave her at the office working by herself. She has friends at the mall and they prepare a set up for an opening, but it is sabotaged over night.  Her sister regrets mistreating her sister unknowingly towards the end.  Also, one of them may have been adopted or they may have been switched at birth.

Any help would be appreciated.

The plot you describe is a very usual in Korean dramas with 50+ episodes. Take a look in the link behind.
 I remember  drama  " Glass Mask" with similar plot.
 the sister there was a underwear designer and she wanted to take revenge from her sister. I hope I helped you and its the one you are looking for.
http://mydramalist.com/5187-glass-mask

Hi Louloudi,

It's not glass mask.  The father was not a murderer.  It may have been something not as popular I believe.  Like the taiwanese secret movie that seems good in my opinion, but doesn't seem as popular
https://www.youtube.com/watch?v=epGzQRUMxlM&list=P...
The only drama I can think of that is similar to that is Jang Bo-ri is here. However, it doesn't exactly fit your description. 
I'm pretty sure I'm wrong because some of what you described doesnt fit, but maybe Her Legend? But I think they knew they were sisters...
I can't shake off the feeling of having seen this drama though. It sounds very familiar to me for some reason.
Hey,

Thanks for trying to help... No luck yet.   The girl has a couple of friends that stuck around her, helping her out.  Once she moves with the wealthy family I think her friends thought she betrayed them....
Her Legend does seem similar, but the actresses of the drama/movie I'm describing were younger and didn't know they were sisters
@Sunah, any other ideas???
@LilVermin, It may have been a movie, but since youtube breaks them down into parts I may be confusing them for episodes/a drama;  However, I doubt it was any where near 50+ episodes; I'm thinking it may have been from Thai, Taiwanese, Japanese, or Korean
@dfanz2 ....  Now that u mention it, the scenario u describe sounds very much like many Thai dramas ..... Unfortunately, I cannot think of anything specific ....  Post in the lakorn section and see if u get a response .... 
Also, u can try Asianfuse forums since many lakorn experts are there. 
Sister sabotaging other sister & sister doing as if she's poor is part of the plot of High Society.

Sister mistreating other sister also happens in Rooftop Prince where both sisters think they're not related (just became sisters by adoption+marriage) but are actually sisters.

Both dramas don't fit your exact description however, sorry :(
^Thought of High Society too (I didn't watch it so I don't know much), but didn't she only have that one friend? And I think they knew they were sisters I mean she kept going home...(I only saw like 2 episodes though)

I can't think of much else, sorry. But Googling lead me to 2 random dramas which I doubt you're looking for, but doesn't hurt to mention: Women of the Sun and Glass Slippers (really old). 

Hope you find out soon, it's annoying when you can't right? xD
Your description sounds like Autumn Tale to me.  The "sisters" were switched at birth, and it comes to light during the drama.
Those are not it.  The girl was apparently the true biological daughter and the mean girl was adopted.  The biological daughter had friends though that helped her through the drama.  I don't recall how it ends or it was a movie split into parts in youtube.  The girls did work in an office type setting.  Let me know any other thoughts.  Now I see that there are too many asian dramas and not all of them are big hits so they become obscure over the years although they may be really good ;(  Any other ideas?
I have come across this drama here on MDL! I can't remember the name either but if I recall, I will post it here.