From the LW's side, though, her response also seems a little overboard. I could explain it by just being offended by the manner of the request (demand), probably... but a willingness to make accomodations for invited guests' food requirements at parties seems logical and polite to me, from my experiences as a child. I didn't even have food allergies, but surely everyone knows some people who do?

And the way Barb and the LW present the food prep rules seems to inflate how difficult they would be to follow, to my mind. I mean, you don't have to use a grill or any particular surface that is difficult to de-glutenify to make gluten-free food - you can just say the grilled thing isn't safe but X, Y and Z, which you prepared in dishes and with utensils that went through the hot cycle on the dishwasher, are! It really doesn't seem like such an extraordinary amount of hassle for the host, compared to the whole-kitchen decontam you'd have to do if someone allergic was living with you. Why wouldn't she just pick a few dishes that can be prepared safely to label as such?