Spoiler....
She literally f's with all the guys (and later the girl- even tho it was forced). She leads Taesok on for awhile and dates him later for a short while just to cheat on him with Hyomin.
Hyomin transferred schools and changed his number + address, but he somehow left a note for the mc to see and she went there (while with Taesok) and they kissed (i think even had sx) but from there on she keeps leading Taesok on while dating Hyomin behind his back, at one point she starts to like the (i forgot his name but the first guy - the victim of Hana). It was just a lot, she annoyed me a lot there because i really liked Taesok, he changed for her and showed care (plus literally beat up her dad after he was abusive to her!) But she ran back to Hyomin:/
God i read this whole thing (the raws) and holy crap did i get annoyed at her at the end.