My puppy won't eat for three days now and is dry heaving. She does drink a little water, but now is throwing up stomach bile. What could be the problem, and what can I do to help without a vet visit?

How old is the pup? Why no vet? She could die, you know. If this is parvo, she will die without hydration and probable vet care.

Congrats. You just got a puppy. Did you think that it wouldn't need to see a vet? I really hope you thought about things that can go wrong.. this is one of them.
Please take your dog to the vet. You bought the dog - you committed to it. Now take care of it.