I really dislike this kind of story with a girl being in an abusive relationship and the other being there just to be an emotional support... It's so frustrating ! And it's worse when the abused girl fucking know that what she's going through is not normal but still legitimate the actions of her abuser. I know she is manipulated or even blackmailed but...
Instead of feeling sorry for herself and blaming her crush to love a douchebag, the MC should help her out, even though it's mean being hated by her. Better that than founding her "broken" after years of abuse or worse, dead. In this kind of situation you have only 2 options, help the victim or leave !