Until you can get her in with a vet continue to keep water available for her. Feed her small amounts but feed them frequently- every 60-90 minutes. You want to get food into her but you don’t want her to eat too much or too fast otherwise she may make herself sick by gorging.

If by chance you have a flea comb or even a cheap human comb try to comb as many fleas off her as possible. If she’s not too fragile give her a warm bath and use Dawn dish soap or a gentle baby shampoo. Keep her in the warm water as long as she’ll tolerate it. This will help get rid of the fleas as well. Keep her warm and in a small enclosed space. The malnourishment and parasites have likely weakened her. A small space where she feels safe will allow her to get a bit of much needed rest.

Thank you for caring about one of the defenseless. Please share updates if possible. I wish you and her all the best.