In my experience, the friend who cannot rise above such situations is not the friend I thought they were: "I can't force you to join us and be uncomfortable, and I will not be forced to choose who I invite. No hard feelings." — Yosef Baskin 44 secs ago

It rather depends why you invited the ex. Did you invite them before the breakup? Do you have a friendship with them independent of the relationship with your "somewhat close friend"? Do you know why other people are saying they won't come if she is there? Without this information the question is much too broad. If you add this, you can ask "how can I respond to people who tell me they don't want her to come?" or "how can I tell her I don't want her to come after all?" or some other interpersonal skills question that is not "what should I do?" — Kate Gregory 1 min ago

I accepted the other answer as it was just a smidge more applicable to my current circumstances but this advice was also very helpful, and I'll definitely keep this in mind in future years! +1 for multiple ways to address them - thank you so much! — eurieka 37 secs ago

I see. Thank you, Jon! — Frank 2 mins ago