I really wish that Joss Whedon had just gone ahead and made the fact Anya is autistic canon. It's heavily implied throughout the series. We're made, at first, to think she's just an ex-demon, but more and more we see that her demon friends don't act like she does either, and then came the episode where we find out she's always been like that, even when she was a human before becoming a vengeance demon. She's always been loud, and literal, with special interests (breeding rabbits, then being a vengeance demon, then capitalism), and NTs were always annoyed by her. There's more evidence in canon of her being autistic than Dumbledore had evidence in canon of being gay, far more in fact, and I wish they'd just come out and said it, given her an arc of seeking and getting a diagnosis.
Especially now that I'm seeing myself in her even more when re-watching the scene in "The Body" where she goes from seeming okay and asking uncomfortable questions to breaking down about how she doesn't understand how Joyce can just be dead, revealing she keeps thinking things like "Joyce will never have fruit punch again." The only thing I didn't like about that episode is I don't recall Willow apologizing for her outburst.
Dang, if they'd gotten her a diagnosis, it would have finally connected with that episode really well.