Oh gosh! Has the vet not come up with anything else other than her UTI? Maybe she has lost her appetite because of the Cipro? Why did the vet change from Baytrol?
Have you tried mixing boiled chicken, or even chicken livers, cut up with a bit of her Hills diet? Do you give it to her in small amounts several times a day?
I don't know what to recommend, but I couldn't by-pass your question. You might try feeding her baby food in syringe, just to get some nutrition into her system.
Have you ever heard of Goji Juice?
FreeLife Live It! : GoChi, Chi3 Energy, Daily Edge I have given my dog this for different problems. It is expensive (about $50 for a 1 litre bottle) but I've heard many stories about how it helps dogs. Especially seniors. You can put a capful into their water dish once or twice a day. That might help some.
Sorry I couldn't be of more help! Good luck to you and your fur babe. :)