“I’m not a part of her social life”

I’ve been with my partner now for about 14 months. I find it quite difficult to accept how secluded her social life is. I’ve only met her best friend twice (once properly) and whenever she goes anywhere, it’s always without me.

I understand that sometimes when she goes out with her girl friends that I would naturally not go. But every work event or get together is never open to partners, and I feel as though I’m a separate part of her life. I feel as though I shouldn’t be irritated by it, but I can’t help the way I feel. I’ve not really discussed it with her. I’ve mentioned it in a passing conversation but she brushes it off and just says ‘go out with your friends on the same days.’ But I don’t want to set up extra socialising events just because I’m not invited to anything she does.. Am I being unreasonable?