My son went through this phase around the same time. It was only when he was giggly/excited that he would ever bite (usually me!). But it is just a phase, he is now 23 months old and no longer bites. I didn't really do anything different than what you are doing too...I didn't agree with biting back, and I couldnt' get angry at him since he was only 'playing'. I just firmly told him "no biting", and walked away. She will stop eventually