Gener norms are a tricky business and it's something that affects us all, even when we would liked to claim that it doesn't. People do have a very strong tendency to conform to expectations, including gender norms. Those norms are in a constant flux and they are very different in different cultures and in different times. If people would just stop and think and try to remember, they'd realize gender norms have changed even during their own lifetimes. And still, when talking about the differences between men and women, people are very keen to explain everything with biology, not with social issues. Because if it's all down to biology, then the current state is okay, and nothing will ever change nor should change. Because change is scary.
I did what Pyrrhus suggested, I ignored the norms and I 'just played'. But how many things had to push me into that direction to make me a gamer, when so many other girls did not?
I was born into a family of two brothers, no sisters, and a mother who wasn't very feminine, so my surroundings was unusually masculine. My brothers were much older than me, so I got all their boy toys to play with. My best friends were a super girly girl, a tomboy, and the boy next door. I learned very early on to go between girl and boy cultures. My father actively encouraged me into gaming. He bought me games and subscribed me to a game magazine. I was also very attracted to games since early childhood, anything from playground games to board games to video games. I've always been unusually individualistic and cared very little of what people think about me.
I don't think any girl could have had better conditions to ignore what gender norms say about gaming and 'just play'. But even I didn't escape them completely. I still avoided the more violent games because those were 'for boys'. I'd never played Doom if my brother hadn't literally sat me in the computer chair, started the game and told me to try it. I had one girlfriend who also played games, and only because she had a brother who had practically forced her to try out some games. She would have never learned on her own that she liked gaming. I still remember when we were gleefully blasting enemies in Doom together. That's a common memory for boys in my age, but very uncommon for girls. Gaming just isn't a part of teen girl culture.
Even as an adult who is so aware of gender norms, I sometimes surprise myself by falling into the same 'this is for boys' trap. For example I initially I completely ignored the release of Neverwinter Nights because the advertising was using heavily sexualised images of a female character. I never gave a concous thought to those ads. I never got upset or offended or disgusted because of them. It was not a case of boycotting something because feminism for social justice rraaarww. I just simply skipped everything relating to that game because my subconcous had already tagged the game 'for the boys'.
Funnily they probably used those images in advertising because everyone knows that sex sells. Sex probably does sell games. It also unsells them to others.