Please Help, urgent

My cat has been gone for about a week and a half. We thought she had died, but then while I was at work, my mom called saying that she had turned up on our porch. I picked up some nutracal and high-energy kitten food from the pet store I work at. We have been giving her the food tonight, and she is hungrily eating it. She is so thin that you can feel her bones. She is weak, but can get out of bed to eat. We have also been giving her water via syringe in her mouth. Is there anything else we can do? The vet is currently closed right now. She is 15, and has FIV.
Thank you.

oh my... besides being weak, does she have any other symptoms?

I'd say to get her into the vet ASAP. After being out on her own for so long she could have been exposed to any number of things that could cause her to be so thin and sick...with her FIV it could be very serious. At least she's eating, that's a really good sign.

someone else will come along soon who will know much more than me. I'm so glad she came home!

I think you are doing the right things until you can get her to a vet. Keep her hydrated, let her eat, but I would give her small amounts often, so that she doesn't make herself sick eating too much at once. Get her some kitten food when you can - that will get her weight up again faster. And of course, she must go to the vet as soon as possible.