i do kinda feel bad for yeonju, but you're really gonna ignore the first person you see?? When you care about both of them?? COME ON YUHA.
In regards to yeonju, she can be selfish, but she really isn't the worst female antagonist I've ever seen, she just seems to be severely depressed. The person that she trusted and loved and gave everything for just told her that everything she did was worthless and ugly. And yes, she shouldn't base all her worth on the words of an a-hole like that, but she did, and, as one would expect, it led to the decline of her self-esteem and her mental health. And now she feels like a weight, a third wheel causing trouble for her friends, a couple who could be "having a good time if they didn't have to worry about her." Still a liability, but a pitiful liability. I think what she needed was therapy, not a trip with friends(which sounded like a good idea, but who could have known how much of a wildcard yeonju could be)