I wish I had good advise but will leave that to the pros - but you are her angel and good luck with your new yorkie - they're very smart and can learn in time to trust people but it's going to take lots of patience -
I correspond with a woman in England who found a yorkie in the snow who was Badly abused ...and that yorkie is now a beautiful well adjusted darling - You can go see her story at this link and I have her email address if you ever have questions - she loves to talk about Precious.
The Story of Precious
to all of you who rescue - you are hero's.