I don't know how traditional this is, but when I eat in Mexican restaurants, I often have grilled vegetable fajitas. I've never noticed any chilis in those. And I usually ask for extra guacamole to go with my meal, and I don't think I've ever noticed any chilis in any of the guacamole I've had either.

Good luck to Mrs. Santa. I have some food allergies myself, and I know how difficult it can be to find something to eat in restaurants.