Contrary to popular belief, cats are pretty easy to train.
The key is consistency. If it is "love bites" then the easiest way to curb the nipping is to remove attention from her when she nips. Pet her nicely, and when she nips immediately stop petting her. If she nips again (to get you to pet her more) gently put her on the floor and walk away. Do this a few times and she will figure out that nipping stops the petting. That way, too, she doesn't associate petting with punishment (like water or noises).
Does she nip when you are petting her tummy? Does she do it after you've been petting a while? Some kitties are very sensitive and petting can lead to over-stimulation where the pets can actually become painful, and tummies can be extra sensitive to begin with. (I have one kitty who would probably rip my hand off if I tried petting the tummy!) Watch her for signals that she has had enough - eyes dilating, tail twitching. It may just be a matter of training you instead of her.
You don't say how old she is, but she may be teething, too. Is it more like chewing on a finger? If this sounds possible, have a small stuffed animal close by to give her to chew on as an alternative to you.
Hope this helps! Let us know if these work, and I'm sure others will have suggestions, too.