if your current dog hates animals why would you put them through the stress. your yorkie comes first, if my dog and cat didnt get along then even though the cat was 50 bucks and the dog was 1200 bucks the dog would go because the cat was here first. if you were to get another dog you would probably have fights in your house every day and the bad behavior would rub off on your lab.
your best bet is to meet with the breeder at her house and bring your yorkie and see if they get along, even the slightest bit of aggression is a sigh to you that it was not ment to be. like i said before the yorkie comes first!
hope i helped!