Ducking Out: yay or nay?

Hello, I think tomorrow will be a pretty yucky day.

I had plans to go to a one day festival thing with my kid for months. It's something my 20s y.o. kid is into, not me, but going to hangout and whatever. Well, they invited s friend to join us last week. So, now I get to go to an event that i don't want to go to and get ignored (because that makes sense.. new friend vs. mom. I'm frustrated by this and honestly a little hurt. I really don't want to go (more now than before).

Question is should I duck out or honor my commitment?