MIL and FIL host Christmas every year. My BIL has been with his new partner for just over 3 years now...
The woman has a DS from a previous relationship. BIL adores him and is very involved in his life, he doesn't see his dad. The first year they were an item, they spent it desperately (she spent the day with just her boy). The following year was spent together, they saw PIL's day after Boxing Day I believe. This Christmas is the first that I know they're definitely together as a proper little family and I remember BIL recently mentioning it'd be nice to all be together this Christmas Day.
PIL's are big show offs and absolutely make a huge deal of hosting Christmas Day and getting everything in, from the grandest of turkey to the very littlest details such as every guest's favourite beverages, any drinks they like, they insist nobody contributes and they take great pride in providing the whole thing.
I had a long chat with MIL today and I asked if Christmas was as usual, she beamed and said of course. I then said it would be lovely for BIL and partner, etc, to be there this year and she said "Mmmm
"
I asked if there was a problem and she told me they weren't mentioning an invite to them, as after all, the boy has a but allergy and their stuff might contain nuts!
I said couldn't she have a nut free day? She said no, it was simply very demanding and probably a lot more complicated than 'one would think' since lots of things contain nuts.
I left it at that but AIBU to think this is bloody well outrageous and mean? Surely one day isn't that hard?
I feel so sad 
DH thinks I'm being OTT and overly invested but I haven't actually said anything...