smack her, HARD, on the nose and say NO! in a deep, menacing tone. React the same way every time she comes back at you. If a puppy bites a sibling and they want it to stop, the sibling squeals. If a puppy bites its mother and she wants it to stop, she bites it. She doesn't injure it, she doesn't cause it agonizing pain, but she does give a nice firm nip, usually followed by a stern growl. Emulate the mother.

If the puppy cries, gets a pitiful look on its face, and slinks back, you did NOT just break its heart and make it question the health of your relationship. That's the puppy's way of showing obedience and apology. It's like sign language.