I had this, too, a few years ago, although it wasn't a new mix, just snobby parents who were bigger bullies than their kids - and apples often don't fall far from trees. Unfortunately, though, there's nothing much you can do - it's their party and they can invite, or exclude, whoever they wish. Rise above it and use it as a tool to teach your daughter resilience and kindness. I was, and am, lucky that my daughter dances to the beat of her own drum & really didn't care that she was left out for other people's parties. However, it was having invites to her own party turned down, ignored, or no-shows from people who said that they were coming that hurt more. I would grit your teeth and plan something fun with your daughter on that day.