The thing about Kim is not because she left, but more about how she left. I thought the whole this relationship thingy was to talk to your partner about stuff; how hard could it be to say "hey MC, my father is a huge jackass and he would cause trouble if I stayed any longer."
She just left; simple as that.
Not to mention, she explained her leaving AFTER their ACCIDENTAL meeting at the company. She could've at least told someone about her reasons, hell, she could have even texted MC and explain everything, but no. She decided to keep the boy in the dark and let him have self-destructive thoughts of maybe he is the reason she left.
So yeah, fuck Kim.