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.