****Desperate Situation****What to do with a feral cat with feline Stomatitis who won't eat?

I have a feral cat that was diagnosed with feline stomatitis. This started 4 months ago when she stopped eating. I took her to the vet where he has given her a shot of Depo Medrol and and Depopan (1/2cc of each) and along with amoxicillin that I am to put into her food when she starts eating again. Usually within a 24 hour period after getting the steroids she is able to eat again. She stays pain free for about a month and then stops eating, but once she gets that injection again she is fine. I've been doing this with her for 4 months now and she stays pain free for a month. This last time, being the fourth time she stopped eating again and the shot only kept her pain free for about 11 days (took her to the vet Dec.1st and by Dec 12th she stopped eating). So again I took her back he gave her another shot and gave me Prednisone liquid to put in her food on the 9th or 10th day.. Well the next day after her injection she ate half a can of moist canned food and now it's the day after that and she won't eat at all again. Is she now immune to the steroids? Can anyone suggest what I can do to help her. She is a feral cat so i cannot give her anything orally at all, she will bite or scratch me. I can only put it in her food and now she won't eat. HELP!!!! Also she won't drink any liquids at all since this problem started 4 months ago. Are there foods out there that she would absolutely be attracted to to eat? I've tried baby food, sardines, tuna fish, yogurt I even put the fish in a blender with water for a smooth consistency, but nothing works, she won't eat any of these things. I'm really concerned because she gets the water she needs only from the food she eats and if she is not eating that will affect her kidneys. If anyone can please help me at all I would appreciate it. Also, I've contacted the vet and I'm waiting for a phone call back. If anyone knows of any questions I should ask him, that would be great. I've looked up this disease on Google and everyone is suggesting tooth extraction. If that was the answer would it be a full tooth extraction or partial? All I know is that her condition is severe. Thanks to all who can help me..