I've had this sort of awkward situation arise at work and I need a polite phrase to help quash it.
There's a group of women that I refer to in my head as the Mean Girls Club (MGC). They very much act like some of the clique-y middle school girls we're meant to be teaching. By that, I mean that they make a point of doing things as a group and making sure everyone else knows about it. I figure this is their way of saying "we are part of this group, you are not, neener neener." They even have a name for their group. I wish I were kidding.
This year, one of them (Sally) had a baby. I was (shockingly) invited to the baby shower. TBH, it felt like a gift grab. Sally works in the same department as my DH but we really share no connection beyond that. I RSVP'd no to the shower. A few weeks later, I was approached by another member of the MGC and she said, "You know, I wish you had come to Sally's shower. We would like to start inviting you out with us and the shower was a good time to see how you interact with the group." Uh, what? I felt like I had missed the royal summons or something. I told her why I said no (DH and I actually had a sports tournament that weekend so I could not have gone even if I wanted to).
So now I have been getting some invitations and more pressure from these people. I don't want to hang out with them! Individually I can deal, but I'm not 13 and so not interested in this sort of pack mentality dynamic. I don't want to be a part of their little club so I can feel superior by excluding people, and I really think their actions at work are unprofessional and in some cases downright ridiculous. As pushy as they are, I feel like it's mounting to the point that I'll eventually be asked outright why I'm snubbing their invitations.
Summer can't come fast enough.