Keeping details a bit vague to avoid outing myself...
I met a group of women - six of us - a couple of years ago through a shared interest, let's call it a running club. We set up a Facebook group, chatted regularly and frequently arranged meet-ups, both to go running and increasingly for social meet-ups. The group really bonded and we have supported each other through various ups and downs.
Often only a couple of people can meet but we've always invited everyone in the group.
However it's become apparent that one person is arranging meet ups with one or two others without telling the rest of us, then dropping references into our Facebook chats ('oh Moira, forgot to ask where you got those new trainers from?' type of thing).
AIBU to think this is a bit rude? Or should I just accept that friendship groups inevitably splinter up?