MC is annoying. She is supposed to hate vampires since they killed her parents, but right from the begining she feel that ML is "so nice to her" even tho he is clearly not.
Because of him, her school life turned for the worse and to make it even better he threatened to kill her brother if she didn't obey him! Even if she was unnaturally attracted by him because he is a vampire, that should make her hate him even more!
When I read a story, I like to understand the characters though, but her reactions are so unbelievable, that I can't read it. I was waiting for MC to tell ML she hated him, to hurt herself from going crazy from this situation. It seems more reasonable than playing lovers with your parents' killer.