Congrats on getting her back!
But if she is really skinny/malnourished, feeding her so much may cause her to die, due to slow digestive systems and being malnourished the rat may rot in her. I'd feed her a small rat every week, maybe five days but I had someone tell me to feed my malnourished python a small rat every week, then after a month start feeding her two small rats or a medium rat if she will eat them. Weigh her every week or every other week so you can tell that she's definitely gaining weight, also may want to take pictures so you can see the progress. If she isn't gaining much weight after a couple months, you may want to do what someone else said and scrounge up money and call around for vets.
Hope this helps!