It just seems incredibly odd for there to be so many lines in a book about gender insisting that there is no way to refer to someone (in the English language, at least) without implying gender. She even mentions the possibility of using „it“ at one point!
I’m liking the book otherwise, but every time the narrators ponder about pronouns without even considering „they“ I have to ask myself if there is any point in ignoring it or if she genuinely just forgot. I don’t think it’s possible for her to have not known about it considering how well-read she was and how long it’s been in use.
Singular they has been part of the English language since the 14th century.
It has not been part of style guides since the 14th century, however. Starting with the dumb “grammarians” of the 18th century it was frowned upon very heavily in the “professional” sphere to the point that for all practical purposes it was expunged from writing by the time of the early to mid 20th century. It still existed in the spoken language, sure. Kind of like “ain’t”. But it was viewed as an uneducated stance and people who wrote had its use practically beaten out of it. Kind of like “ain’t”.
“it was cool before so let’s keep doing it” can’t do all the heavy lifting here. You need something else.