It's always hard to try to analyze this, because it easily turns into stereotypes, but I will still give it a go.

When boys get stressed and confused, they may act out. Girls might turn that feeling inside instead and develop anxiety.

Girls might not get into femininity while boys, well the can act "neutral" gender wise and never be questioned.

It is said that Asperger girls have less special interests, but in reality they just have more socially acceptable ones. While boys might be extremely interested in trains (stereotype! sorry!), girls might take an interest in the life of an idol/book character, do art, music and do creative writing or develop an interest in pets.

It is also speculated that girls in general have more social pressure on them and that would go for the girl with Asperger's as well. That might explain why she is sometimes better at social situations than boys.

Baron-Cohen is a pretty smart guy and I like most of his stuff but I am very critical to his autism quizzes as they do have a gender bias.

Here is from his AQ test:

I usually notice car number plates or similar strings of information

I am fascinated by numbers

I am not very good at remembering phone numbers

I am not very good at remembering people's date of birth

Of course some aspergirls are interested in math and science, but some are more drawn to language and details of language.

If I try to imagine something, I find it very easy to create a picture in my mind

When I'm reading a story, I can easily imagine what the characters might look like

I find making up stories easy

I don't particularly enjoy reading fiction

I find it very easy to play games with children that involve pretending

If an aspergirl indeed has a vivid imagination, she will score low on this test and not seen as having as many autistic traits.