Congrats on your new puppy! Nice to have another male in the yorkie forums.
Anyway, the reason she is biting is because no one taught her any different. It is recommended that yorkie babies stay with their mom and litter until they reach 12 weeks of age. In fact, the YTCA pretty much has it as a rule all of it's members must follow. The reasoning behind that is mom and litter mates teach the puppies proper doggy etiquete, one of which is bite inhibition.
Misha is home now, so you have to step in and fill that role that mommy and her litter mates were suppose to. Yelp, squeal or say ouch when she bites and stop all play. If you continue to engage her after she bites, she'll think biting is an acceptable form of play.