AIBU

The first thing to do is find some more friends. Real friends do not act like this.

After that I would say nothing. I would block all their numbers, unfriend them on Facebook and any other social media. Ghost them. There is no going back to friendship after behaviour like this.

Book yourself in to the brunch place, and go and enjoy it, reclaim it as your own experiance and ditch the awful “friends”

So they all agreed to "sneak off" , exclude you from the usual group activities and say nothing!!?? Are those REALLY friends?

Lollipoplove, I'd be inclined to ignore all of them, 'do or say' nothing - and find new people to form a group with. Perhaps the birthday girl still has a problem with you and invited the others?

Well they re no friends are they as Monica says find some new ones I d definitely leave that group without another word

The advice is what I would give my teenage GD. Find some new friends and ditch the others as not worth your friendship.
Are they grown ups? Doesn't sound like it to me.

Perhaps she is jealous of you?
I had a ‘friend’ who wrote me a very strange letter a few years ago. She showed my reply to the ‘friends’ who collectively replied in a horrible way.
They had one side of the story, had probably had too much to drink when they thought it was a good idea to act like they did.
Luckily they don’t live near me. I showed the card that they sent me to everyone I could and got it out of my system.
Then crossed them off. Who needs friends like that? Not me.
Hope you feel less hurt soon?

Say nothing, simply block them out of your life. Totally.
Very unkind.

I wouldn't do anything that showed I was upset. I would just gradually withdraw from the group of 'friends' and put them in the 'acquaintance' group. I wouldn't offer any support or help to them. I would make plans vague and be very noncommittal. They then have nothing to gossip about. These are not good friends.

I think that I would say something to the effect that you were hurt that you were not invited to your 'find'. Having had your say I would then look for other people to socialize with, these people do not seem to be very friendly to me.

I think you should comment on the post so that they know you have seen it and can't accuse you of being surly about it. I'd say something like 'How lovely to see you all in your finery for X's birthday. So glad you enjoyed the venue I recommended.' Before you throw the baby out with the bathwater re the friends I would see what happens when you next see them and the excuses they come up with. Some may genuinely not have known you were not invited. However, I think you have to accept that 'Birthday Girl' still holds a grudge and maintain a frosty atmosphere when dealing with her. Good advice from most posters about widening your circle of friends.

Thank you all for such good advice. I was thinking the same but getting clarity ale at s helps xx