I have never dealt with aggression or protectiveness that may be fear-based. Perhaps she needs more socialization with lots of other people and perhaps she needs to interact more with the other family members than she has been doing. I can only say "perhaps." I don't know the situation. I might suggest you go to the "Training" section and look over past posts to see if there are any threads that seem close to your situation. Our member, ARCHIE, won't be on until tomorrow morning, but she has used a trainer for some issues that are similar to your yorkie's. You might send her a message and give her the link to your thread and see if she has any suggestions. Only a thought. Good luck and don't give up.