I wouldn't bite her back. If she starts hitting/kicking/pinching etc would you do it back to her as well?
She could just be doing it for attention, even negative attention is attention to a toddler. I'd try to teach her that teeth are for biting food only, explain (she might not understand at the moment but it doesn't hurt to start) that it hurts and we don't bite other people, and when she does it simply remove her from the situation.
It is a stage most kids go through, and the more you make a big deal out of it the more she is probably going to do it.