It's definitely a puppy thing -, but something you'll need to keep working on in order to get it under control. Most puppies learn bite inhibition from their siblings and momma, so you have a bit of extra work to do
My suggestion is to stop all play, altogether
if she starts to nip and bite. Get up and walk away. She should soon learn that nipping/biting = play/fun ending. The trick is to be consistent and have EVERYONE on board.
Good luck! I'd love to see some pictures too