These women are not 'dense.' They knew exactly what they were doing. Going out, keeping it a secret, and deliberately excluding the OP. And then parading the night-out photos all over social media. I have seen it done before - to someone I know. My cousin. She was in a friend group with 2 women at work, 2 ex employees (who left late 2022/early 2023,) and a couple of the ex employees friends. 7 altogether.
All was OK for about a year, and they shared a whatsapp group, and they had nights out every month. Then the 2 women at work were under investigation at work for something, (around June this year,) and were suspended. They both asked my cousin to speak up for them, give them character references, and go to their disciplinaries and defend them. She said as she still works for them she would rather not, as it may compromise her position there.
Then she found herself frozen out of the whatsapp group. The group went silent, even though it was still active. They had made a new one, and no-one was chatting on the old one. They went out without her - and put pics all over facebook. Because she hadn't done what they want, they froze her out. So she unfriended them all and blocked them all on facebook, instagram and twitter. And she blocked them on her phone. (All within an hour of seeing the photos of their night out.)
The two women were sacked some weeks later, and she heard nothing from them again. ANY of the 6 women. She said she would rather die than say 'hello are you still my fwends?' They are absolute mean girls. She was well rid.
@BlueNavy As has been said, just unfriend and block and find new friends. There HAS to be a reason why they have done this, but I doubt you have done anything 'wrong.' The Queen Bee in the group has probably discovered her husband fancies you or something. Or, as a pp suggested, it's something to do with your kids falling out. It will be something like that.