Something similar happened to my wife and her friend. They had been good friends through childhood and beyond and kept in regular touch--at least once a month, and get-togethers a few times a year. When we got married, my wife's friend was one of the bridesmaids. But when the friend got married, we weren't invited to the wedding. We were invited to the "engagement party" though. She gave my wife a lame excuse that it was family only and that it was her mother and aunt that were organizing the whole thing and that she really had not much say.
My wife was a little hurt, but more bewildered than anything else. Although my wife was not going to let the day pass and not watch her friend get married, so she told her we would go to the actual wedding ceremony (it was at a church) even if we couldn't go to the reception. Hey, it's a public church so anyone can technically go to a wedding--even the homeless guy sitting on the stoop! The night before, the friend gave us a lame half-hearted invitation to the reception, saying someone else had canceled and that we were welcome to come. We made up an excuse that we had already made plans for after the ceremony. And the clincher is that when we went to the ceremony, we saw plenty of "friends" that were also going to the reception, so not as "family only" as she first said.
We behaved very civil and nice, because ultimately we were happy for her. We still gave her an engagement and wedding present. The friend seemed to feel guilty cos a few months later we were invited to a family lunch for her birthday. We figured it was her way of making amends, so we went. Although the lunch ended up being a bizzare, uncomfortable experience that has yielded many stories to share with friends and family!
We still see her every once in a while during the holidays or if she's in town. The whole thing was just weird.
