I have my guys on a hypoallergenic diet, but it's homecooked. You could try Wellness kibble - they make single protein/single carb foods:
http://www.oldmotherhubbard.com/well...ons_index.html
For now, I'd stay away from chicken as a meat source entirely. The nutritionist I use for my Marcel has this cool looking product for allergies, check it out:
http://www.askariel.com/pages.asp?pid=allergies (click on ProAller, that's the one I'm thinking of).
Allergies are so frustrating, but if you can truly put her on an elimination diet with some supplements, you just might be able to get to the bottom of it.