I accommodate all allergies not food preference and I do run a peanut free daycare. If you do not want to provide this get parents to bring the food with it labeled. If she shows up to daycare without the food then send her home with the child to get it then come back. If they ever give you are hard time about making them go home to get the food just simply say you didn't prepare enough food or don't have the type of food needed to accommodate the allergy because it was understood the parents would provide.

Normally parents understand and don't want their kids to be hungry so I don't think you will have a problem.