It's not mc's fault tf...
Jeongwon seems to really care about Hwayeon just not in a romantic light. Up until then they've displayed a friend with benefit type of relationship, truthfully that's all I think they are. Nonetheless hearing that she was jealous must've been news to her causing Jeongwon to feel partially guilty? Idk I mean she even apologized.
Anyways the one truly at fault is Hwayeon. She's so controlling and on top of that, manipulative.

THE BROWN HAIRED GIRL NEEDS TO STAND UP FOR HERSLEF CAUSE WTF WHY DOES SHE KEEP ON HOOKING UP WITH HER ROOMATE WHEN SHE CLEARLY LIKES THE MOTERCYCLE GIRL AND THEN CONTINUES TO BE PUSHED AROUND BY HER ROOMATE WTF!??!?!?!??!?!?