I cannot believe how quick most of you are to judge Hyejin. You would be flustered too to realize your feelings so suddenly, she was able to spend all this time with him solely as a friend. As Yul said, she's confronting her true feelings just recently. It's natural to hide when you don't know what to do, we are not perfect.
She's now wiser and know she's hurting him so she will try her best to be assertive as she has shown us so far but she's also human so let her breath and figure everything out naturally.
Edit: forgot to say this cause I got mad over the comments but as I was bathing in the feel good atmosphere, that creepy senior had to appear again. I literally let out a screech when I saw him, doesn't he have a life of his own? It's not like they publicly humiliated you so just forget about them, dude.