I've worked in a community organisation for a year. A colleague had a milestone birthday at the weekend and turns out they had a party where everyone was invited except me, including staff who started after me. It was definitely deliberate, not an oversight, because I had been asking her on Friday what her plans were and she was really vague "Oh you know just socialising..." On one hand, obviously, I'm a grown up who didn't get invited to the birthday party, boo-hoo, big deal and grow up. She's an adult and can ask who she likes, and it wasn't an official works do. On the other hand she is not particularly good at her job because when she started it was a small organisation and it mushroomed past her capabilities, which she openly admits, and I spend a lot of time helping her out when she comes to me, even though my own job is really stressful and she should really be helping me! I have taken her side when the boss had been asking her to do things which she doesn't feel able for, so I feel a bit hurt. I went on a holiday last year and brought her back a little gift, because she does try hard, and because she is basically a nice person. I've never had a run-in with her or felt there was any bad feeling. And to add insult to injury, I was the one charged with organising her card and whip-round for her gift! I felt embarrassed this morning to realise I was the only one who wasn't asked to go and a colleague who I get on well with was really mortified about it and doesn't know why. I'm not asking her why I wasn't asked, because I know it's not that big of a deal really. I haven't been off with her or anything, I wished her Happy Birthday, gave her a hug and made her a cuppa. (Ok maybe secretly I'm trying to shame her into feeling bad 
) But deep down I'm stinging. AIBU to be a bit upset?