Just a small thing - but have you tried taking the other approach? Instead of trying to change how she treats her body, how about changing how you feel about it? I don't mean to be rude or anything, but how about trying to see the sexiness of it?
I know hair isn't everyone's thing, but it doesn't have to be horrid! It's just a small mental adjustment, and before you know it, hair is sexy!!!
Having said that - and please, it's just a suggestion, you can't make yourself like something if you just deep down hate it - having said that, it sounds to me like the essential problem here is her own self esteem. Once she is comfortable with her body and with who she is, only then can you really discuss modifications like shaving with her.
And the secret to improving her self esteem???
There isn't one. At least, not that I know of!
It just takes time, patience, compliments, compliments, time, compliments and lots and lots and lots of love. Keep telling her how much you like it, keep encouraging her to be proud of herself and who she is. Try and make her accept the body she's been given, and make sure you tell her how and why you find it so incredibly sexy!
Best of luck, please keep us updated!
CasperTG