It does sound like she is slowly responding to the vet's treatment. It is unfortunate so many puppies get such a bad start. I hope she continues to improve. I encourage people to adopt from shelters. While it is true, there are too many sad stories where even after expensive treatment, the puppy doesn't make it; but there are many more stories of people enjoying a greatly loved companion they rescued from a shelter. I hope yours will be one of them. You vet is your best source of info on her progress. I often discourage tempting a dog with rich food. In this case, I would continue exactly what the vet says. As she improves and gains strength, then it will be time for the discipline of a dry puppy chow and little else.
At times I may seem to be harsh with people that don't spay/neuter their dogs. The puppy you are struggling with is the result of somebody having an unspayed female they allowed to become pregnant. That couldn't have happened without the availability of an unneutered male. At some point the puppies were exposed to distemper. I so hate seeing good people such as you being put through the wringer with a puppy you want to have to love, because of others' irresponsibility. I can't see how anybody that know and loves dogs, can help but be very concerned.
A thank you to J_9 for properly posting your PM to the dog forum where people with more dog experience can respond. Site policy encourages such. In this case, I am not sure we can do much except encourage you and urge you to work with the vet. As she improves, you may find some of the material in the sticky useful. See
https://www.askmehelpdesk.com/dogs/i...tml#post251802 You can always post back with specific questions.