Totally agree with Rollercoaster.
If your girlfriend was understanding enough of your passion, she'll be supportive, just like you would be too, if it were her interest.
At the end of the day, both parties should come to a compromise if they really want to the relationship to work out. If it's one of those "me, me, me and only me" girls, then you're better off legging it alone.
My girlfriend and I used to quarrel a lot about me spending a lot of time on music, but over the years, we've managed to make a lot of compromises, and almost five years on, we're still together.
She still goes to all of my gigs, but it does help that she's nuts about SRV, Satriani, Dream Theatre and Los Lonely Boys, among others.....hell, I'm a lucky guy! :lol: