Try this:
As soon as her mouth touches you and you feel a bit of teeth there, say in your deepest loud voice "ouch!", rather than pulling your hand away (which makes it a fun play toy), let them decide that "ouch" means you bit me... and that's bad... The idea of the deep loud voice is to startle them away from you, then the second there is a release reward with a proper toy (this technique comes from My Smart Puppy, a great book for puppy owners).
It's kinda cute how it ended up working with Harley, for some reason every time we'd say ouch, he'd stop, lick me then take the new toy... now if I feel his teeth ever, he always kisses it better.
