beta
For not saying she likes Yeonwoo ... There's this thing some mature people do. It's called thinking before you answer and taking care not to lie to other people just to make things seem fine. Lying is usually very disrespectful, though most people make it seem like it's nothing.
She clearly likes him but she doesn't seem to know what the feeling is, especially in a romantic sense. It would have been worse if she had told him yes when she wasn't sure if it herself. Some people are naturally not very in touch with their feelings, and there's nothing wrong with that, but I'm sure her past has a lot to do with it too.
I still feel sorry for Yeonwoo, of course. I feel sorry for both of them. But maybe try to hold off on the judgement until you see how she ended up like that in the first place.