My heart goes out to you. It must have been so awful for you.
I heard a story just the other day, and I can't rememhber the name of the breeder or where they were from, but the story was, that they got this tiny Yorkie that they had paid a fortune for and after they got it, it grew like crazy, so the belief was, that the breeder deliberately starved her to keep her tiny because people will pay more for a tiny one. This story had a happy ending, but still,
How horrible to think that anyone would do that.
I have decided that when I have puppies, people will get a book on Yorkies when they make their deposit, so they know what is normal and what to watch for.
Good Luck to you on what ever you decide to do. I have a feeling if you tell her that you are contacting a lawyer, that she will replace your puppy AND pay the shipping free of charge.
Jeanie