Had plans to meet dsis (my age, 23) which we told our other older sister about (28). Although we're close to her and all live in the same city, tend to see older sis less as she is married and does a lot of stuff with her dp; also I don't think uni-style parties etc are really her thing anymore, especially as she lives about an hour away and her dp is late thirties and they do a lot of stuff with older people in couples.
Anyway older dsis heard we were meeting and said to let her know where we were. Fine. I ended up seeing friends and getting quite tipsy early on, then contacting younger dsis (who I had firm plans with) to let her knoe my location, who joined. Older dsis was bored at home as her dp was out drinking so called me a few times, but I barely registered as was drunk/silly and also she definitely wouldn't have come out; we were really far from her house and it was clear she only wanted to see what we were up to as she was bored ie on her terms - plus we didn't have firm plans.
It has recently transpired that she's still upset about this. I apologised but don't think I did anything that badly wrong! Who ibu? I think she's upset that me and younger dsis see each other more - but that's only because we have more free time/no dps and lots of mutual friends. Feel a bit angry she's made me feel bad about it