How old is your daughter? Does your doctor think that the headaches may be caused by allergies?
There are many Ensure type nutrition drinks and maybe you will find one that is dairy free and also and most importantly taste good! You can also blend strawberry flavoring and Cool Whip which is dairy free.
Citrus will be the hard one because many products are made with the unrefined products of citrus.
We are seeing more labeling for wheat and it is surprising what products contain it.
Avoid Honey as an alternative for children because it has a very high level of botulism that some kids cannot tolerate. It is a total taboo no-no for babies and toddlers.
Cream of rice is a good replacement for wheat.
I hope this is just a temporary diet. I don't know which could be harder teaching a child to wear glasses or asking them to give up their favorite food.