You are totally right. They are deep characters. There's also so many people hating on Chanwoo just because of what he likes to do. But he is being such a trustful person. I love both of them.
Yes, thank you! Clearly her ex had spent so much time tearing down her self esteem to the point where even having logical emotions, like being upset about something is blown out of proportion and called "overreacting", it makes someone hyper aware of how they're being perceived and so much more complacent because you don't want to seem "crazy" even if they're valid emotions.
Ihyeon's ex is a narcissistic manipulator, and afaik no one else knows aside from Chanwoo that the ex is making moves on her.
She's been outcasted because of her ex, and it seemed like no one else was by her side to tell her that none of it was her fault and she was completely broken, which is why she's still so traumatized. She's extremely sensitive of other people's emotions because her ex manipulated her into becoming that way, just look back at the flashbacks when they were still dating. This seems to be the reason why she still can't outright refuse her ex's favor now, because she's a pushover and he's still manipulating her (push and pull)
Healing isn't instantaneous, it looks like it will definitely take time with Ihyeon who seemed to be alone this entire time. Sometimes, you just need another person to knock some sense into you.
Right now, Chanwoo is exactly that person. He's trying to build her confidence, first instance is telling her she can take the lead in their fake relationship, and then second when he tells her he wouldn't go with to the outing if she says so (but she sadly declined). Ihyeon they could never make me hate you