Dehydrated puppy. How do I help her get her strength back?

I have a six week old great dane puppy. She's the runt from the litter and she got dehydrated. So we brought her home and have been taking care of her. She won't eat at all and won't drink very much (I've been giving her milk replacement I bought at walmart.) I took her to the vet the second day i had her because she's very thin. They wormed her, gave her a liquid shot to help her with the dehydration and gave me some antibiotics to give her once daily. It's been 3 or 4 days since I took her to the vet and she doesn't seem any better, she is so skinny and weak it kills me to see her like this. Basically my question is how do I fatten her up so she will be healthy again? Is there a certain kind of liquid I can give her because she won't eat solids or wet food at all. Thanks ahead of time!