Unlike actual men and women, transmen and transwomen like to refer to themselves as "boys" and "girls" respectively. My guess would be that this person is a trans-identified, possibly non-binary female.

That sounds about right. Trans is frequently used as a way to reclaim some youth, by pretending to be more innocent and naive than they actually are. To roleplay as someone fairly young and still discovering themselves. But they usually get it all wrong about the other sex.

When it comes to actual boys and girls, they're less likely to refer to themselves like that unless they are very young. (Especially males, who would probably prefer other terms, like 'guy')

I feel like these types of screenshots should be collected and sold as a puzzle book where you flip to the last page to see the answers.

Oh yeah; like some Encyclopedia Brown book for Adults.

Using your knowledge of genderwoo and from the clues provided, What was their actual sex and sexuality?

Turn to page xx for the solution.