I have been using a book called Let the Dog Decide. His theory is they are associating it with something negative as you speculated.
I vote you change it to Pebbles
and see how she does. I firmly believe training (yorkie or otherwise) should always be done positive with lots of praise and treats. It has worked like a charm in my house.
Then you can join the soon to be newest club---Peebles Club. It already has 2 member lined up.
