High expectations of friends?

So for example, my friends were going for brunch with one of their friends they haven’t seen in a while and at first I wasn’t able to go anyway because I had to bring my daughter to dance. They had a late start and I told them well I’ll meet up with them there. My cousin, one of the friends, told me that she already told them our other friend was coming and didn’t want to overwhelm them and will meet up with me after. Bullshit excuse right. Anyway shit like that pisses me off and more people ended up going anyway. Am I wrong for being pissed? Or why is it so hard for people to just be decent?