AITA for wanting to surrender a foster dog whose owner isn’t contacting me?

I agreed to foster a dog for someone I know through work. I was told the dog would need fostering for 3 months. It has now been 6 and the owner only communicated with me the first week of the foster. I have messaged them multiple times since and have never received a reply.

The dog is a good girl. She’s old though is starting to show signs of needing more vet visits to maintain health. I called the vet information given to me for her and they told me they would need to hear from the owner if I were to be able to get any medication prescribed for the dog. Problem is of course that the owner is been AWOL since the trade off.

I FEEEEEL like the A because I do care for this dog but realistically, I can’t afford her and I work too much to be able to give her the more constant care that she needs. I worry about surrendering her and her being put down. I was happy to help someone in need temporarily but this has gone on much longer than I was told.