I have a friend who I haven't seen for ages as she lives in a different town. She's going to be in town and we made plans to meet up tomorrow night. I get a message from her now saying 'Hope it's ok but I've invited X to come along too'. X is a friend we both know and who lives in my town but we've never hung out as a trio or anything and since I haven't seen this friend in a while I was really looking forward to catching up one-on-one. I don't know X that well either and so wouldn't feel comfortable talking about personal stuff in front of her. But she's already asked X along...so it's presented as a fait accompli and I can't really tell her to uninvite X.
AIBU to think you don't just invite a 3rd person along to a pre-arranged catchup? She will be seeing X separately anyway so it's not like she's in town for one night only and needs to catch up with everyone all at once! I have another friend who often does this - you think you've agreed to a nice catchup and then all these other people are invited along. Am I being overly precious?