If you have a no-kill shelter near you please surrender the kitten there since they have access to veterinary care. This kitten is probably inundated with parasites, and probably hypoglycemia and needs supervised medical care. If a no-kill shelter is not available please try to find the next best thing.
You don't mention the kitten's age, but a very young kitten's digestive system may be too immature to handle cat food.
I'm not the vet, but I once tried to rescue an abandoned kitten that was not quite weaned. One of the most important things to do with young pups and kittens is to keep them warm - like 85 degrees. If they aren't warm enough, they can't digest food well. My little kitten didn't survive and died in my lap.
I don't like the signs you describe, so don't be surprised if she doesn't make it. It really would be great to spend a bit of money to have a vet assess her and give you a better idea of what to do to help her. Best of luck to you both. :-)