Along with your vets antibiotics you may want to ask about regualar electrolytes given to her.
I buy the electrolytes from revivalanimal online

http://www.revivalanimal.com
I have packages of it and mix it with water when i feel they are a bit dehydrated and not drinking enough.
I put it in a NON needle shringe and slowly give whoever needs it 2-3 milligrams 2-3 times a day for 2-4 days as needed.
When cats get liver problems or any problems from getting older sometimes they need extra fluids...they need a lot of water at that point in their life and if their not drinking it...i usually help them with the electrolytes.
Only once in a while.Not on a regualar basis.I wouldn't do it regualarly without the vets permission.
I always have it in the house for when i see a cat look sluggish.
It's been a blessing having the powdered stuff on hand.
Mix 1/2 tsp of electrolytes to 1/4 cup or 2 ounces of water.
leave it in refridgerator and discard after a few days.