K.E.
Sounds like the diet problem is with baked goods. Homemade pancakes do not need yeast and thay can be used in place of bread for sanwiches etc, Rice cakes should have no yeast. Tortillas, crackers? Read the labels. I think yeast free breads do exist but I cannot give any brands. Are you looking for prepared foods or are you ( or is she) willing to cook yourselves?
More important, WHY is she allergic to yeast? In my extensive personal experience as a former allergic mess, the cause of the vast majority or allergies is toxic build up that the body cannot eliminate becuse the liver cannot perform adequately. Are her allergic symptoms recent or long standing? Recent could be caused by mold or similar toxins/exposure which hits the liver so hard that it can only handle a fraction of its duties. Long term could be caused by a diet that does not provide the liver with the necessary nutrients to work with.
There also exist allergy elimination techniques like NAET. I am not a fan of them used without addressing the real causes of the development of allergies, but they can have a place in allergy management. Try Googling NAET, which stands for Nambudripad's Allergy Elimination Technique. But this method can be very time consuming and ultimately expensive, so I would use it as a last resort. I need to find out this site's policy regarding personal contacts, because I know a lot of remedies for a lot of things, but I cannot tell what is most likely to work for an individual without talking to them or seeing them or a picture of them taken when they are having the problem