My friend's cat who is about the same age as yours has kidney failure. About a month ago they went throught the period of not eating too. They needed to force feed him for a few days when all of a sudden he started to eat on his own again.
To force feed make a paste of canned cat food or baby food (beef or chicken) with water and if you can get a tube of Nutri-cal that would be good to add to the mix. Draw it into a large syringe (no needle) and squirt it into the cats mouth small amounts at a time. At least she will be getting some calories into her system.