Have you checked with whomever owns the puppies to see if they are suck at all?
This would really have me concerned especially due to her age, her barely drinking, vomiting and being lethargic. I would strongly suggest you get her in to the Vet if you haven't already. Any suggestions I might give you may be only a band aide on something serious.
Have you tried maybe some boiled chicken and rice? It is important she have fluids.
other information : she has been drinking a little water, but not much. She looks like she is really weak and is not doing anything but laying around. No coughing, sneezing or any other symptoms.
We had 4 little puppies visit and spend the night two nights ago. She was fine before they came. Since they were here (they left yesterday morning) she has been acting this way.