Lock her in a room
Psh. You don't. If your girlfriend is a gamer, that's damn hot. If she's good... send her to me and i'll play her.
Learn to please her a bit and she might not need Halo anymore.
Maybe you should start playing the game as well...
Or maybe the dork who posted this is a big fat liar who fantasises about a girlfriend who plays halo and is playing out his sick fantasy online.