I want to take a golfing trip to Ireland with the boys - my girlfriend is inexplicably fuming that I have not taken a trip with her in the year we've been together. Should I have gone overseas with her first?
She wanted you to
to go with her first. Don't play dumb.
Please don't mistake this for an endorsement of inexplicable fuming, either. If she has something to say, she should say it.
Maybe I'm wrong about what she would say; for all I know, you broke promises, or she's controlling, or had some unspeakable childhood incident in which she was brutally denied a golf trip to Ireland.
But here's the thing: There is a general power structure to dating. Even when the ultimate goal is commitment, the person who asks someone out has, roughly speaking, two intermediate goals: getting sex and avoiding humiliation. This gives the quarry real power, since s/he decides unilaterally who achieves these goals.
Thanks to evolution and/or socialization (discuss among yourselves), men still are largely the initiators, so I'm going to assign genders just to avoid a he/she/his/hers political-propriety pileup.
So. Once a woman commits to a man, especially if the relationship is sexual, the power shifts. Now it's her turn to fear humiliation. She doesn't want to learn she has committed - in other words, surrendered her power - to someone who was only along for the ride. She is deeply invested in a man's investment in her, even if she has her own doubts about him.
Which is why a trip to Ireland with the boys when you've taken her nowhere could lead to fuming you don't comprehend. She might not even be able to defend it logically. She is simply off-balance and is reading your behavior for signs of how high a priority she is. And I'm guessing the ambitious boy bash was not a good sign.