What was the reaction like? Was the vampire mentally like an adult and what age if yes?
I looked it up to refresh my recollection. Shori is 53 years old but looks like a 10 year old black girl. She is mature in how she acts—not like a child. My reaction when I first read it wasn’t to feel weirded out on behalf of Shori. You’re in her POV and Butler establishes her maturity as being commensurate with her true age. There’s still the fact that her partner is physically attracted to what appears to be a 10 year old girl, which shaped my view of that particular character.
Knowing Butler, she isn’t doing any of this without careful thought and a reason. She’s trying to reflect something about society back to the reader. We know black children are more likely to be hypersexualized and perceived as older than they are, and consequently are often treated differently from white children. Maybe she’s flipping that around and presenting us with a situation where we know the mc is a wise, smart 53 year old. How much do we respect her autonomy based on her appearance?
In a way, many of these vampire books could be seen through this lens, whether intended by the author or not. How does society view the sexual lives of young women (or older teens) in comparison to males of the same age group. Why are we content to watch Buffy go through physical and emotional trauma of fighting demons every night but see a line as crossed when she ends up in bed with Angel? You can look at this sort of thing through the lenses of a puritanical history, patriarchy, and possession and control over women’s sexuality and sexual expression.
All of which is why it is important to remember these are works of fiction and have to be treated as such. They can be vehicles to explore ideas, and a questionable relationship in fiction may be trying to tell the reader something or force the reader to examine the world in a certain way. They don’t have to be (and certainly should be assumed to be) endorsements of such relationships in the real world.