A vet reference wouldn't mean that much to me because there are a lot of bad vets out there. There is a puppy store in my town that has vet references for their puppy mill pups.
A reference from another person who supposedly has purchased from her -- how would you know that the person isn't a relative or someone else who would say anything?
I definitely would not purchase a puppy that is going to be shipped without tons of really good evidence verifying that the breeder is legit and has high standards. I also think small puppies should be transported in the cabin of the plane with a human escort -- especially in this hot weather.