From what I know, the reason why women/girls are diagnosed less is a lot to do with the socialisation of girls at a young age. Basically, girls are taught to play nicely, share, consider other people, be gentle etc...

The way I was brought up was trying to put uber femininity on me - i.e., my mother loved to put me in dresses, and buy me dolls etc. I would scream and scream and scream if she put me in a dress, to the point it was easier just to put me in trousers. My uncle was around a lot when I was a kid, and because he didn't have any kids at the time, used to spend a lot of time with me. It was also to do with my father being so ill, so I didn't have a male role model etc. My uncle didn't really care if I was tomboyish and asked him a lot about cars, or wanted to go 'playing rough' i.e. toy guns, climbing, doing things that got me dirty (I'd come home constantly with ripped trousers, muddy shoes, twigs in hair etc...). So I think I was allowed to become less and less traditionally feminised to the point where Aspergers traits really began to show - impaired ToM (this probably was worsened by my being an only child with no peer group in my neighbourhood), lowered empathy, poor understanding of social norms etc. I can remember being in high school, and other girls hated me, but boys always got on with me because I'd talk to them normally and usually had quite similar interests. One girl, who had a thing for a guy I spoke to in school, attacked me in class one day because she was convinced I also felt attracted to this boy. No amount of denying it got through to her.

Anyway, I always had/got the assumption that because I'm gay, that explains why I'm tomboyish, and why I have quite masculine interests. Which most lesbians would tell you is nonsense - I don't know a single other lesbian who is even remotely as into gaming as I am, I don't know any who are into computing, and ultimately, they're still women, who think like women. The latter part causes a hell of a lot of trouble for me, because most people who know me say that I have a male brain. I understand how guys think, I react to things in a very 'guy' way, I do 'guy' things - to the point where my male friends quite literally treat me as 'one of the boys', regardless of whether I'm in jeans or a skirt. Maybe if I was heterosexual, I wouldn't have felt so alienated because guys genuinely think I'm cool, and I'd understand how a male partner thought/felt. Whereas with women... jeez. I don't get them, on any level. Most people find that quite hard to believe, but I can't grasp concepts like... I've pissed her off, so I really should let her go calm down. I think "well no, I have to fix it, so she stops being pissed off". In the end I usually piss her off even more because I keep reminding her of what I pissed her off about in the first place, and I don't get why she's mad, because I've fixed it... right? Even typing that, it makes utterly no sense to me, because if people do something to piss me off, and then fix it, I don't feel pissed off anymore. Its a lot more simple... but apparently women are a lot more emotional...

For me, it was probably feeling that inept that made me wonder if there really was something that different about me. I just don't get it. Its made worse, because I am a really caring, compassionate person, who does genuinely try to do the right thing, especially when I've done wrong... and I mess up.