I recently attended a party with my DP, for his child. His ex also attended with her partner. DP is very amicable with his ex, knows her partner reasonably well as he moved in with her last year so sees him a lot at drop off / pick up. He also still helps her out with some things around the house as he does that for a living.
They split up around a decade ago and I'm the first partner he's introduced to his kids / his ex.
I was a little nervous going to the party and meeting the ex but DP told me it'd be fine, she'd be friendly etc. I get on well with his DC.
I was introduced to her partner first who was pleasant. DP then introduced me to his ex who smiled but immediately walked off. Over the course of the evening his ex pretty much refused to acknowledge or even look at me and on a couple of occasions I even caught her and her friends talking about me. Afterwards DP said how surprised he was that she wasn't friendlier as they get on so well, and he's made lots of effort with her DP.
There is another event coming up soon with the same people going. Would I be unreasonable not to go? I felt really quite uncomfortable and I don't want to have to put myself through that again so soon, but I also don't want to upset DP by saying no to the invite.