get her to ask them why they hate you. also writing a letter would be a good idea, but keep it simple. thing is though, if she's been brought up with those parents, she won't wanna do something big like move out or defy them alot, because shes been brought up to respect their authority. but sreiously dude find out the reason they dont like you, if its racism, fuck em, (or their daughter) if its something you can negotiate on, give it a try, but dont back down too easily, theyre not so high and mighty.