You will want to switch to a grain free with a novel protein. Novel proteins are ones that are not commonly used in most dog foods. (Currently chicken, lamb, pork, beef, duck, and salmon are the most commonly used and the ones a lot of dogs are allergic to.)
My allergic pup is currently being fed this:
with bison and that + a new peroxide shampoo has worked absolute wonders on his skin, and no real tummy upset. (I know it says it has grains in the description, but the bag is accurate and says grain free.)
They also have other recipes but you just need to look for a novel protein. Current novel proteins that brands are using are: Bison, alligator, boar, and venison. Since they're lesser used than the usual meats, your pup is less likely to be allergic to it as she has never been exposed to it to develop an allergy.
I hope that helps!