A bit of a long one.
I'm a step daughter, my DD and his wife have been married for 25 yrs. My Stepmum has a son who has 2 children. My DD and my DN'S spend every Saturday together, and my eldest DN is in the same class as my DD. We are close. It was my youngest DN birthday today. So my SIL , my Two DN's and my SM have all gone out on a day out without my DD. They invited my DD to breakfast but were then going out together. We didn't go for breakfast . So AIBU to think this was a bit shitty?