Trust me its parvo, I had a litter of puppies and I thought the same thing, because they would get better. But they had it and I had to get a couple of them put down, luckily not all of them had it. If she isn't to bad and not really dehydrated then you just need to take her in to the vet every morning and receive a shot for about 4-6 days. It will cost you about 14-16 dollars per shot. So might be able to get rid of the parvo for under $100 dollars which is great, because once they had it and get over it, they can never receive it again. You just need to make sure that she stays very hydrated, I would mix in gatorade or pedilyte with her water to make sure shes not getting to dehydrated.

I hope everything works out and good luck.