This question has come up before. When a girl makes a statement like that, it's because she's feeling threatened or neglected. We don't like to feel like we're competing with something/someone.
Why not try to get her involved? Show her how to play, let her play a few cheap SNGs. My husband was the one who got me interested in online poker, and now I play more than him!
If she's not interested, and if you really care for her, then make time for her. Playing while she's out of the house works, or when she's sleeping, like Stick suggests. But the key is making time for her too. A girl likes to feel like she's special to the one she is commited to. It doesn't have to be diamonds, just a little time and effort on your part.