I mean I can't exactly blame her for going somewhat crazy after getting brutally murdered like 16 times (how many times did she die already?) in a row and being the only one thats aware of whats going to happen in a couple of hours. Especially since everybody except Jeha doesn't even look human to her in the first place.
But still.
Barging into a class and beating a student to death with a chair without explanation won't give you the ending you want either, Chaerin.