Please help me. My puppy is very sick and I don't know what to do. She isn't eating and has lost a lot of weight the last 24 hours. Im afraid she will die before the vet opens tomarrow. Help!

Get her to an emergency vet clinic. They can at least try to stabilize her condition. Then you can take her to your vet tomorrow first thing.

How old is she? What are the other symptoms? Is she able to hold down fluid? Is she vomiting? Blood in the stool? If she cannot hold down liquids and there is no way to get her in before tomorrow I would suggest making a rush to the store for Pedialyte and orally giving it to her in frequent intervals to try and hydrate her.