You are in California, so do a search for the Puppy Lemon Law. Coccidia is a parasite that is transmitted from dog to dog and can live in the intestines for a while. It tends to act up during periods of extreme stress (like moving a puppy from one home to another).
The incubation period of coccidia is 13 days. So if she was only in your home 8, then she picked it up from the breeder.
http://www.dogplay.com/Breeding/lemonlaw.html