I have celiac disease so I can't eat wheat rye oats or barley. Some of the grains I eat are Quinoa, Kasha (buckwheat), Amaranth, Sorghum, flax, and potatoes. There are some tasty Quinoa pastas out there. PM me if you would like more information on some of the brands.
Ener-G foods are actually pretty good and free from many allergens, but I am unsure about rice. that is a really hard one to be allergic to.
Food For Life is another brand that has many "allergy free" foods.
My nephews are also plagued with pretty nasty food allergies, as is my sister. Unfortuneately, none of them are allergic to the same foods. I am not sure what exactly they eat at her house.
I would encourage you to try some of the more non-traditional foods,like sweet potato chips, amaranth cereal, etc.
Potato starch can be used to supplement recipes that call for cornstarch.
Are these allergies she may grow out of, and can she be on a rotational diet?