It was an eye-opener to me when the language therapist systematically tested my - apparently highly verbal and communicative - DS's abilities and found the deficits. They were mostly the usual ASC ones - nonverbal language, pragmatics and emotional expression - plus a few idiosyncratic ones, like becoming non-verbal whenever he wanted something. But I wasn't aware of any of them until she pointed them out -- and I'm his mother.
So I can't imagine how the average social worker would be able to tell for sure that someone didn't have an ASC.
One of the dangers of using our own experience is that ASCs vary so enormously. Autism can be a thing of opposites. One child can be academic, anxious, articulate, intense, angry, another can be distracted, pleasant, sweet natured and forgetful. I've met or heard about quite a few high functioning children with ASCs (DS's friends, other kids in his therapy goups, my friends' kids, ASC charity work...) and they're still full of surprises.
One of my siblings thinks she has autism, but her childhood (and to an extent her adult) behaviour stemmed from trauma.
And people can have both. Having an ASC doesn't let people out of experiencing trauma. My mother had always thought that my father's unusual behaviour came from (very real and horrifying) childhood trauma until my DS was diagnosed and my mother learned about ASCs... which made her re-think. ASCs can run in families. Your DD has one. Don't dismiss your DSis.
There seems to be an overlap between ASD and attachment disorder traits.
Yes there is, and we're not really qualified to tell them apart, are we?