So is this one of those dramas where the FL likes and hangs out with the SML for most of the drama and then develops…
She hangs out with both pretty equally in the beginning. Towards their college arc which takes up majority of the episodes, she hangs out with both but mainly the ML. But you're right for the most part. She only developed feelings at the end of the drama.
Tbh I understand why she liked cheng leng so much, heck I would too, but for the viewer I think it was dragged on for way to many episodes, even if it's realistic. But if you are into unrequited love, go for it
"Just Kidding" makes you wonder what she was referring to, "just kidding, you will never be reformed." Or "just kidding, your mom didn't die." Either meaning meant he will be tortured by her