Have you talked with the vet about a short course of prednisone? I doubt they would want to put her on it for very long but it might be long enough to get things under control so it would be easier for you to try and find something that helps her.

If you are interested there are some holistic pet food stores on the web...

http://search.onlynaturalpet.com/search.aspx?searchterms=evo&click=5&s_kwcid=evo%20 cat%20food|742301523