Two main points I can think of:
1) You've told all of us hoe you feel about her, but have you <i> shown</i> her how you feel about her? Have you actually gone out of your way to be nice to her without asking for anything in return, or have you done nice things as a prelude to asking her out? She may think you are only being nice to get her, and hence she's not interested - it sounds like she got hurt by this previous asswipe and she's afraid to make the same mistake again. Be really nice, but don't try to ask her out or bed her. Just show her what a great guy you are and how much you really would help her out.
2)Having said that, don't wrap her in cotton wool. My mate and his ex went together quite well, but he always used to insist on walking her home from <i>everywhere</i>, giving her lifts <i>everywhere</i>, and generally going a bit too OTT. She dumped him, saying she needed her own space and her own life back. I'm not saying that as a bad thing, just be careful how strongly you put across your willingness to help. Always offer, maybe saying "are you sure?", but if she says no, so be it - don't force your help on her or it will seem as if you going OTT to impress her, which will only make her think you simply want to bed her.
Lastly, good luck mate - I hope you get her!
