M.M.
Mine is allergic to rice, apricots and bananas among a host of other things. So when she was just starting to eat solids I would give her rice and bananas not knowing that those were the exact things making her sick.
You do have to avoid the unnatural foods. Can she eat fruits, they have natural sugar, fructose, or is it just refined sugars she can't have.
You have to read every label. We have gotten really good at spotting rice, it's usually in the top few ingredients, artificial colors are at the end. I try not to give my daughter anything it takes me more than a second to figure out and pronounce.