I agree with your girlfriend.
Some drug addicts will not stop doing drugs even though they know there is a good chance of dying prematurely as a result of their activity. Same with climbing for some folks.
I liked that article someone posted a while back about climbers, jailbirds, high-risk behavior cases. I could completely relate. I love climbing, but I also recognize that it is the risk/challenge/fear itself I am addicted to.
Of course, I also like being outside, getting exercise, buying gear I don't need, etc.