It's very sad that she thinks a 'normal' childhood should be filled with illness and pain. It's even sadder to think that she'd wish that on her nieces.

You may have to just go with what you know and forgo any further testing. I, myself, have never been tested and don't care to be as it won't affect my diet one way or the other. Freedom from a lifetime of migraines (and apparently running to the bathroom right after dinner, which was always interpreted by my family as a way for me to get out of doing some of the dishes) is more than enough for me to stick, like glue , to this diet!