You know, I've never seen anyone ask for advice on how to tell people that they are a sports fan, or that they are musicians. In both these case nobody even worries if their significant other shares their hobby or not. Playing video games isn't even that unusual, chances are all her past boyfriends played games too.
I play table top RPGs, such as Dungeons & Dragons. When I and my wife first started dating the topic came up of what we like to do for fun. I told her I play video games, read, I'm into computers, 3D animation, and on the weekend I play Dungeons & Dragons. Now I did have some concern in revealing that I was a HUGE nerd. However I also knew that if she decided that she didn't like me because of my interests it wasn't going to work out in the long term regardless. Lucky for me when I said D&D, she perked up and said she had always been kind of interested in RPGs but never had an opportunity to play them. She never did become more that a casual player, but things certainly worked out. We also have many hobbies we don't share however. She never did show to be overly interested in computers or 3D animation, and I really don't like writing like she does. That okay though, some things we do together somethings we do together somethings we do on our own. Its normal