My best guess is that about half of MIT graduates could be called Asberger’s/Autist according to the latest fashionable description.
Asberger’s tends to be a genetic or familial trait, and true Autism tends to generally be environmental or medical misfortune (vaccine injury, etc), and there may be other yet unidentified causes
There are many women who are Asbergers and/or”neurodivergent”, but generally women learn more easily how to hide or mask their interests and intellectual abilities so they will “fit in”, and usually are harder to properly diagnose.
Many of these women, as they age, find “masking” tiring, and superficial socialization is really boring.
Your granddaughter may not be that socially awkward in a group of kids at her own intellectual level. Finding friends who function on her level is very hard to do, particularly in small towns. And teen girls can be truly nasty to other girls, just totally mean.
Various psychiatric conditions also manifest differently in men vs. women. For example, there's increasing evidence that the alleged higher frequency of clinical depression in women vs. men is simply due to it being diagnosed at a higher rate in women. This is partly because depression in men is more likely to manifest itself as anger rather than stereotypical depression symptoms (sadness, crying), and because men are more likely to "man up" and hide the problem.
So what you say about Asperger's being more hidden in girls may very well be true, both because the symptoms may be slightly different, and because there's more pressure among girls to fit in. Contrary to Hollywood teen movies, most of the male nerds in middle and high school were not ostracized or viciously bullied when I was a kid - mostly just good-natured ribbing. In contrast, girls who were perceived as strange were completely ostracized by their peer groups.
Having said that, I'm not convinced that Asperger's should be considered a mental illness in need of any treatment or therapy. Most people with that diagnosis are fully functional, just strange. This is in contrast to real autistics, who are often nearly functionless.