People can be sensitive to things (and sensitivities can change) without being allergic though, allergies and intoleranaces are different things like gluten intolerance and coelliac disease. I assume she has been tested for coelliac?
With a child so long I'd be careful about messing around with diet too much yourself if a dietician could help given her other problems, so you don't unintentionally make things worse, especially if her system is quite delicate at the moment and with her only being young.
Have you kept any kind of diary or food, stresses etc... to try and identify any triggers beyond anything physical?
Can you actually see the spasms then (as opposed to what she says and her reactions)?