Name changed as this could be identifying.
Today was DD1s first proper birthday party. As well as some friends we invited her cousin. SIL replied that she was working but she would get someone else to bring DNiece. That was over a week ago. Today was the last party and DN didn't come. DH contacted SIL and she said she forgot to remind her husband this morning and he probably forgot.
Me and SIL get on fine but have never been pals like I think DH wants us to be. But recently I've tried to make more of an effort - arranged a day out, sent messages just making conversation, etc and as a result I think we've started to build a friendship.
AIBU to feel let down that they didn't come today? We've always gone to DNs birthday parties. I think my recent effort is making me feel a bit hurt that they haven't made the effort.