It works, but by that point, she's fallen in love with the male lead. Maybe she starts to date the guy she wanted to make jealous, but then breaks it off with him to get back together with the male lead.

Probably not really what you're looking for, because it's more a matter of moments than a whole elaborate fake-dating scheme, but both the leads in Suspicious Partner help each other out by pretending to be in a relationship with each other to make their exes jealous / to make them look less pathetic in front of their exes. 

Sorta similar but completely opposite. She “dates” the second lead to make the male lead jealous 

- hi my sweetheart 

 AH:

Probably not really what you're looking for, because it's more a matter of moments than a whole elaborate fake-dating scheme, but both the leads in Suspicious Partner help each other out by pretending to be in a relationship with each other to make their exes jealous / to make them look less pathetic in front of their exes. 


 Amaury1514:

Sorta similar but completely opposite. She “dates” the second lead to make the male lead jealous 

- hi my sweetheart 

I've seen both of these, but thanks.

If I'm not mistaken there's an element of that in Personal taste. Isn't it? I think the ML and FL get to live together which makes everyone (including the 2d ML) think they have a relationship. The twist is that the FL mistakenly thinks that the ML is a closeted gay and using her as his beard.

you might have already seen it, Marriage not Dating. She gets into a contract relationship with male lead to make her ex jealous. She ends up being a fake fiancé, her ex is close friend of male lead.

I just finished Wednesday 3:30 PM and it's exactly what you're looking for plot-wise. It's a very quick and light mini drama.