Have you tried walking her at a brisk pace for 15+ minutes? Also, Ms. Stillwell from "It's Me or the Dog" series has mentioned the nipping and biting behavior is done by puppies but if they're taken home earlier than 8 weeks they haven't been taught by their litter mates that it hurts. If it still continues to make a high pitched squeak that'll divert their attention. I watched her teach the small 4lb. yorkie the other day. He was so cute! And he got it!
I wish you well!
