DD has been referred for diagnosis at 11, we had the first suggestions she might be autistic since she was 10.
In some areas she is more obviously/stereotypically autistic. She gets very anxious and dwells on concerns, has issues with loud noises and busy environments, and struggles with sudden changes to her routine. She sees a lot of things as black and white, and I can see there are some social nuances she just doesn't get. She has obsessive interests that might only last a few days, but boy are they obsessive while she is in the middle of them. She has always had a habit of repeating parts of a sentence several times while she waits for her brain to catch up. School have said her pro-social score is low, though that isn't something we have seen much, and she can struggle with eye contact when she is overwhelmed. More recently we have had a few shutdowns, which have cemented for us that the suggested diagnosis is probably right - you can see how she sometimes gets to overwhelmed by the noise in her brain that she just switches herself off for ten minutes. She also stims - hand wringing and flapping when she's very stressed, or more quietly just popping joints.
However, she doesn't have a huge amount of the more stereotypical traits - no sensory issues, eats anything and everything, no obviously repetitive behaviours, no real sleep issue etc. Has plenty of friends and makes new friends easily. While she would be thrown/upset if she turned up to a class and found she'd been moved table, she has never needed a routine and can be easily pulled away from one task and set off doing a different one.
With hindsight, she was always an enormously "quirky" child who had a very formal vocabulary and seemed to live in her own world - not daydreaming, just (to quote Betty Draper) she very much marched to the beat of her own drum.
DD says the more she reads and learns about autism, the more it resonates with what is going on in her head. But it isn't always apparent, she masks spectacularly well a lot of time, and so the issues we see now quite obviously relate to the exhaustion of masking for so many years and not knowing who or how to copy now all the girls she knows are becoming such individual personalities. (I've been told girls can mask very well when they are younger because there is a more obvious 'basic' personality of a 7yo girl to copy, for example.)
The diagnosis makes a huge amount of sense and even without the formal diagnosis, all the teachers we've met at her new secondary school say she very much is autistic, it's just sort of quieter, and harder to explain , than some other presentations.