Dear Abby: I’m tired of friends extending our invitations to people we didn’t invite

Dear Abby: We have some dear friends with whom we socialize a lot. However, it seems that every time we invite them to do something, they invite others (whom we know) to join in. Our latest invitation is to visit us at our lake house for several days. They would like to bring their adult son and his girlfriend. While we like their son a lot, we do not know the girlfriend.