In response to your anecdotes on social behavior:
-I see what you are saying regarding perspective-taking. That is certainly a plausible explanation for the meltdown. Did his results also perhaps not comport with how she has historically related to him? If what she has been offering him as communications of love is quite different from what he turns out to identify as his preferred mode, then accepting his results would also have required her to confront possibly having "disappointed" him (even though, as a parent, he probably received all of her offerings in the spirit in which they were intended; but she might not understand that from her perspective as a child, purely for developmental reasons).
-That's a thought-provoking hypothesis, and a good observation.
-As far as playing highly-organized and detailed school...well, that was DC1! Except with younger siblings, with whom DC was quite persuasive (so much so that DC2 was a bit disappointed with the excellent preschool teacher who followed this experience). We apparently had insufficient numbers of children (for DC1's purposes!), so there were a lot of imaginary students in the class too. And DC1 is quite far from being on the spectrum. Your DC may or may not have had willing or fully-engaged participants (we don't know one way or the other), but it isn't impossible that they actually thought it was fun.
-Playing with younger children does usually suggest some level of social skill delay, so yes, that's something to watch, but children with ADHD also often have social skills delays, since you really have to pay attention all the way through interactions in order to learn how to navigate them.
-Also a valid point to watch. But also, some precocious (GT or otherwise) children don't fully recognize adult/child boundaries for other reasons. And, again, it's not uncommon in children with ADHD, for the reasons already noted.
Bottom line, these are all worth watching and storing away as observations, but not really definitive either way. (Not that helpful, I know!) It's particularly challenging to tease out both ADHD and ASD-like symptoms in females, as both do not always present the way they do in males. And, of course, most of the research literature is still on boys...
If the ADHD becomes better managed, you may be able to start to see some clarity over time.
