Sister in law has always just helped herself to stuff in my house - generally food from the fridge or cupboards. It's her old childhood home. She has had a bit of a tough time and dp has always asked me to ignore it for his sake and not "make a fuss" about it.
She now has a 2 year old and a husband and they came yesterday for Christmas dinner. I cooked for 14 people.
2 year old has a number of food allergies. I was aware of what had allergens and what didn't. The problem is sister in law helped herself to food before we even sat at the table. It was busy and hectic and I realised after the event that she had taken a load of food for her daughter in between me taking it out of the oven and before I had placed it on the table.
2 hours later, she announces she's leaving early because dd has got hives and must have eaten an allergen and they have to leave to get her antihistamine.
I should also say I had noticed she had a face like a slapped arse from when she arrived and I wonder if there was another issue.
Either way AIBU to tell her to not help herself to anything in my house again without asking.