I'm going through something very similar, so I understand what you are having to deal with. Like the others, I don't consider it to be aggression, just a high-energy puppy.
My older dog, a very laid-back non-aggressive submissive Maltese, has trouble putting the puppy in her place, but she does eventually do it when she has had enough. We watch the two very closely, and then let the Maltese rest on the couch so that the pup can't get to her. It has gotten better, but we still have a ways to go.
Just imagine what a Yorkie pup does when she sees a tail with long hair wagging back and forth ... that's just something
begging to be attacked in her eyes. She never saw a tail moving around like that when she was with her Momma and liter mates.
