I can understand that you feel hurt and left out, given that you have never met your wife's work friends before and were not invited to her birthday gathering despite the larger number of attendees. But I think it's also important to consider your wife's perspective and the dynamics of her workplace relationships. It's possible that her colleagues might not feel comfortable with someone outside of their work circle joining their after-work activities, and your wife might not want to put them in an uncomfortable position by inviting you.

At the same time, it's important for you and your wife to communicate openly and honestly about your feelings and expectations. It might be helpful to have a conversation with her about why she didn't want you to join and if there are any other opportunities for you to meet her work friends. It's possible that there might be other events or social gatherings where you could meet them in a less formal setting.