!!!! Yes, you did the right thing! A trainer should educate themselves about different breeds...she should have known that a collar can be dangerous to a Yorkie's trachea (especially tugging at Princess like that!!!). Ugh! Anyone can call themselves a trainer and it sounds like that is what she is doing. What in the world was she trying to accomplish by doing this...making her more untrusting of strangers?! I am glad you fired her.
Tammy