Towards the end, he appears to be typing on some sort of backwards mini-typewriter in midair.
It’s obvious, really - you’re seeing a reflection of the typist in a window. Yeah, that’s it.
Apparently a lot of young people are getting into typewriters.
I always hated them. I could type but I didn't like it. I was so happy when the damn things were replaced by computers, but I can understand how someone who's never seen one could be fascinated by it. It's a machine that you can work and watch and pretty much understand every aspect of how it functions. There's a physical feeling of impressing the letter onto the paper.I have a small collection of manual typewriters, with a couple of them in working condition that I use.
I simply love the things. It might be because I first learned to write (by myself) with my father’s Remington portable… But in any case, I enjoy typing in a manual typewriter. Computers and electric typewriters do not provide the same deep, intimate satisfaction. I won’t comment about typing on an iPhone 
I’ve not read any of her books. Perhaps the mirror references one of her stories?
Comment from Wikipedia: “Her father neglected to register her birth until 1900 and there is some uncertainty about the date.”