I agree with reapectful_observer that we often create that special dish for company and CO wouldn't possibly be able to remain healthy eating like that.
That being said, I had a friend call me in a panic because she was having the CO and wife and DO and wife over for lunch and was given a laundry list of things they didn't want to eat. My friend wanted to serve grilled salmon with a nice fresh green salad but they didn't eat fish and a particular type of vinegar that was in the salad dressing and cheese. She decided she was still going to make what she wanted because her husband loved the meal, the DO didn't have the same restrictions and then also make a few things for the CO. When it was time for lunch, guess what the CO and wife ate? Yep, the salmon and salad that they were apparently allergic to, and they raved about it. Guess they could decide when they had allergies.