I am sorry your pup is sick, your breeder sounded like she must have been decent since she said she was keeping the pup till she was 12 weeks old, what else do you know about her? Do you know much about Parvo, it is normally VERY SERIOUS most pups need to be under 24 hour vet care and many do not survive it. I am hopeful your vet is correct that she is getting better. While I have never had a pup with parvo I would think if I did the ingredients in the dog food for this phase would be the least of my worries. anyway good luck to you and let us know how she is doing
Parvo (Parvovirus) in Dogs: Symptoms, Prevention, and Treatment