@infiniteinterface To be honest, I didn't remember her surname off the top of my head but I remembered that it was mentioned in that chapter where she was feeling dejected about how her co-workers treat her.
It looks like Maya uses her high school physical education uniform for pajamas, at least in summer. That's probably why her t-shirt has her surname on it.
Off-topic, I finally bought Flying Witch on Blu-Ray a few weeks ago. I watched it on Crunchyroll as it was airing and I have been buying the English-language translation of the manga but I just never got around to buying the anime on physical media until I was buying something else from an online anime store and thought I might as well check to see how cheap Flying Witch was, and it was cheaper than I expected (and I'm talking about the Sentai release, not any dodgy bootlegs).