With dd1, it was very obvious from about age 3 because she never played imaginitively with dolls house type toys - i remember at Christmas specifically when she was about 3½ she got a large princess castle with little figures and thrones, furniture etc. And she just did not know what to do with it at all!
She's bright and from about 3, it emerged that she is very, very artistic so she was great at crafts and drawing but not dressing up or playing pretend games.
She was very practical too - no fantasy play or silliness.
And then as a teen - so obvious. She had friends but they'd do bowling and cinema. She never did teenage parties, never experimented with alcohol, never went to concerts. Never did anything that teens do. For a bright girl (straight A student) she seemed young socially at 16/17.
DD2 was less obvious as she was a very girlie girl. In fact she's just getting assessed now at aged 17. She did play with dolls and dress up as a child. She sailed through primary but was insecure in friendships. She did have friends and loved sleepovers etc but never a best friend to share secrets with.
Again, high school it fell apart big time. DD2 (unlike dd1 who was very secure in herself) did want to be like other teens so she did do the make up, clothes etc. Did go to a few parties (very few!) but she hated high school. And it wasn't so much the work - it was the poor discipline in classes. DD2 is not academic. She's bright enough but definitely not in the very bright A stream university lot. When i was at high school, i too was in an average middle stream and i found the mucking about hilarious. But dd did not at all.
The lack of control unsettled her. She found pals in the drama group but never liked hanging about in big groups of peers at weekends. She preferred one friend at a time.
The masking she was doing caused migraine headaches. Eventually it all got too much and she took an overdose aged 16. Just a cry for help, rather than a serious attempt to end her life (8 paracetamol taken) She did stay at school and take her exams, and did well. But now has moved to FE college where she is much happier on a practical course.
She definitely struggles with group teen friendships, and understanding the rules within girl groups. Girl groups (as any NT girl knows!) can be based around gossiping and laughing at people outside your group. But inside your group, you trust those in it to keep your secrets. DD never really trusted those in her group and hated that the group was based around making drama out of others' lives!
But that is the fun of being a girl isn't it. Even women do like a bit of gossip!