Perhaps, I say perhaps because this may not be the case, someone is playing too rough with her. I do know from experience that too rough of play will cause these little one's to be more aggressive at a certain stage. I'm not saying they will always be that way, because I don't believe that is the case with any yorkie.
Secondly, put a big bunch of pennies in an aluminum can or metal container of some sort. When she starts to bite, shake it gently...not too hard at first. If she stops biting, fine. If she continues, shake the can harder. She should quit. They do not like this noise.
Let us know if any of these suggestions work. If nothing works, please take Staci Snyder up on her offer. She is great with these little one's. Cosmo has a wonderful and loving personality.
