have you watched shameless? if so, I was thinking of something similar to lip and Mandy's relationship. if not, basically she kind of had a huge crush on him. friends with his younger brother or sister and kind of did whatever she could to get him to end things with his gf at the time. at first, he was like "this girl's NUTS" but he kind of loved that she was nuts about him. it was probably the least healthy relationship either of them was in. I'm down to brainstorm and work out kinks/details