At that age if one of mine were really misbehaving (like being awful) the consequence might have been "when you can calm down and be kind to us again, you may sit with us to hear the story". (message - if you're unkind, we won't welcome you to join us right now while you carry on.)
I think this is pretty severe, and it's delayed - so she isn't going to put 2 and 2 together. I'm much more into teaching them good behavior than punishing them for something that happened yesterday.
I never expected my kids to include their siblings if they had a friend over. It's nice if they do (and consequently because I never pushed it they tended to play with them part of the time) but it has never been a requirement. They can't gang up on them or be nasty, but playing with their friend by themselves is pretty normal here.
You could use this as an opportunity instead of punishment as more of a "What can we do to make this better next time" kind of learning moment. Our kids tend to include the others once they go outside to play, that kind of thing. I let mine decide between themselves what would work. Make them part of the solution.
This was also at someone else's house right? You weren't there to really observe it. I think it probably should have been dealt with at the time if there was any nastiness. The mom could have pulled out a board game or found a Frisbee, etc. if she really had to. There are so many ways to deal with this kind of thing other than putting it all on a 5 year old.
My child who is older still gets a bit teary from time to time at drop offs - if you had already dealt with upset from day before that morning, she was probably already a bit upset.
A lot for a 5 year old in my opinion. And even my teens - if they are terrible at times - we don't mess with pre-planned big things. I've been angry with one of my kids right up to when we go in, but all is forgotten when we're having a family fun time. I mean, I'm not going to ruin everyone's fun because someone acted up. Trust me if she doesn't go to the show with you, it will be odd for your older daughter and she will miss out on sharing the fun with her sister too.
Good luck :)