[Deadbug]

This is heartbreaking. I know you must be so devastated.

Here's my take, right or wrong.
If the breeder is offering you another dog and you accept it, ask her to please keep it with it's mom until 12 weeks. At least then the pup will have grown a little and be more stable to bring home and you'll be a little more comfortable doing this again.

If it were me and I paid for a purebred Yorkie, there's no way I'd be satisfied in accepting a YorkiePoo in it's place. Contrary to popular belief, a YorkiePoo is a mixed breed dog and the monetary value is much lower. You can pick one of those up all day long at the shelter for far less than you paid for your Yorkie.