Welcome to Yorkietalk, I have learned so much since visiting this site.
You say:
"She states that the mix breed is better than any other when it comes to health reasons."
I thought this was true, but after doing research on this subject it's a bunch of malarkey. If the dog has a genetic fault mixing it with another breed won't help the puppies, the fault can still be passed. For that price you can get a very good AKC registered Yorkie. A good place to start is The Yorkshire Terrier Club of America.
http://www.ytca.org/breeder3.html#AZ
Familiarize yourself on the breed standard. Some people focus on size only and overlook other desirable traits. Also, do a search on selecting a breeder and what qualities to look for. If you have enough money, buy from a responsible professional breeder; don't reward those unethical breeders with one cent. That warranty is only as good as the people behind it.
Nancy