I have a tradition that each year I take my niece (F14) and nephew(M16) to a trip to a nearby city. Both of the kids love this trip. One of my brothers recently got married and his wife has a daughter(F15). My niece and stepniece are in the same grade because my niece skipped a grade and they go to the same school.
My stepniece heard about this trip from the other kids and wanted to come so I decided to take her as well. (Just to be clear all the kids are cousins)
A few days ago my SIL called me and asked me to exclude my niece from the trip. She sounded really angry. I asked why and she said that apparently my niece and a group of her friends have been bullying my stepniece. She said she doesn't want my niece to be anywhere near her daughter. I told her that I understand that she is upset but she doesn't get to tell me who I take to my trip. She kept insisting and yelling at me saying I can't possibly expect her daughter to go to a trip with her bully. I tried to calm her down but not only she wouldn't calm down but she kept screaming until I couldn't take it anymore so I said no of course I don't expect that, your daughter won't come to this trip then and hung up the phone. She thinks I was a huge asshole but I think she was acting very entitled, expecting my to exclude MY niece from MY trip for her