My puppy tested positive for Parvo but she has no signs, what should we do?

We adopted a 15 week old lab/ pit bull puppy from the pound on August 25th, she had been at the shelter for 4 days and she had not been given any shots there. We took her straight to the vet and found out that she had worms, so she was started on dewormer, but our vet didn't want to give her shots yet since she may have contracted something in the shelter and the shots would make it harder for her to fight it. 3 days later we took her back in because she threw up worms the night before (we found that is also normal while being de-wormed.) On a whim he checked her for Parvo and she tested positive, so we started IV and antibiotics, etc. She has been on fluids and antibiotics for 2 days now and still has not shown any signs of Parvo, she is hyper and hungry. My question is when will we see signs? If don't see any signs after another day of treatment do we continue? (Its very expensive.) How do we know when she's better if she isn't showing signs? Please help!!!