From a long interview at In the Margin:
I think that writing multiple genres certainly helps me stop characters from calcifying as they might in a single-genre book. The rules that would dictate who Harrowhark Nonagesimus is and how she functions change drastically when you put her in a horror book and when you put her in a comedy book. Some of these characters are basically trapped in the wrong genre and I like seeing them flail about.
I was in a lot of early video-game fandoms which were at their heart role-playing games, so often you got this big juxtaposition of people who had played the game one way, like they’d made up their team of the male characters, and therefore got a massively different experience to me, who took as many women along as possible. I got so cross as a teenager seeing female characters laughed at or made the girlfriend or the butt of whatever grim joke, when in fact I’d beaten the boss with them, I’d kitted them out to basically kill God. ... I’ve taken that energy, I guess, to SFF. I am simply forcing you to sit down and watch how I play the game.
It is getting harder and harder again, especially for authors from marginalised places or backgrounds, to write works where the takeaway isn’t 'this is to succour all my marginalised people'. For anyone on the female-identified axis this is especially hard because it seems to me that most books by anyone female-adjacent have an expectation that they will comfort the uncomfortable and discomfit the comfortable etc.
And from an interview at Tumblr, this is roughly who she pictures as Harrow:
Amazon lists Nona the Ninth for September 13.