...well. From a girl's opinion, if I was the girl, I would want to know that the guy would always be there, even after I rejected him again and again. Even when I'm at my worst. But don't seem to stalker-ish or anything, cause that's just plain freaky.
And, you have to see her perspective. She gets bullied by her friends, and I'm not even sure how her parents are because you didn't mention. This situation happened with two really really good friends of mine, and the girl's reason was. Because, "Her family and friends would always be there for her and she's not even sure if the guy will" but you just have to show her that you will be there.
Oh, that was long. Hope it helped.