Well, I know I will may get slammed for this and I am not trying to act as if I am more informed that your vet, but from everything I know and have learned, that is a HUGE difference of size in regards to breeding.
There are LOTS of breeders on this site alone--experts on the Yorkie breed and people who have been breeding them for many years who will tell you the same.
Just remember, there are proper courses of action and your girl is not 'doomed' so don't think of it that way. I know you only want what is best for her.
