I don't post very often, but i think I will throw in my 2 cents. I am an avid motocross rider and have been riding for nearly 22 years.
When I asked my wife to marry me, I told here that me and my bikes were a package deal and that if she ever told me I had to stop riding, that would be the day I left her. Not because I love my bikes more than her, but because no one who loved me would try to make me stop doing the thing that brings me so much happiness.
She said that she understood, but that in turn, the day that I started putting motocross before our relationship, she would leave me.
We have been married for 6 years now and I have missed many rides to do something with my wife, and she has spent her fair share of weekends sitting at home while I went to the track. The key is to find balance like slownrusty said. Talk to her and make a plan. If she doesn't understand then so be it. But she sounds like a very reasonable girl, and I think you will come to regret it if you just stubbornly sit back and let her go.