I am afraid it is just trial and error. I don't think fat percentage is too important unless she has had problems with high fat before, although some of the grain free foods are pretty rich. Look at what is available in your area, check your budget and read the ingredient labels closely! Since she is sensitive to both chicken and eggs, I would try to steer clear of chicken fat as a preservative as well. It is pretty common, and usually not a problem, even with chicken sensitive dogs, but if you can find something without it, all the better. FWIW, turkey and duck may be fine, as well as fish based.