What's the deal with prof Van Brun? [huge spoilers?]

[Sardoc]

As the title suggests. (haven't played HH, so I might be oblivious to something that was explained long ago - I don't even know if she was a character in that game)

1) She doesn't know what wiffle bats/wiffle balls are, being a PE teacher. Suspicious much?
2) There is a "do I know you?" moment when the PC first meets her, as if she'd seen him before. Interesting.
3) The PC suspects she might be spying on him when he bursts out of Grabby's office. He of course dismisses the thought quickly, but I don't.
4) Apparently she was in a band in the past, as she might request the chorale sing rock songs.

Sounds like there's a lot we don't know about her? I'm really curious. What do we actually know about her?

EDIT 11/04/2020:
5) She leaves the gym during the first sports club session, and is nowhere to be seen when the PC kicks a ball into Ellen's head. You'd think a teacher would be present in case things go south. What's she playing at?

[MillaMaxwell]

Don't worry, she wasn't in Horse Hall, so you aren't missing any key backstory stuff there. I believe Prof. Van Brun and Ms. Darden were actually created by Kickstarter backers for Wolf Hall.

The glimpse of red hair the PC sees when he storms out of Grabiner's office is explained in Ellen's route. Everything else you listed though is quite intriguing and I don't think there's ever an explanation of her quirks in this game. Hoping she shows up more in a future Magical Diary game!

[Panakaos]

Not to mention the reaction Blaise had to her when she offered congratulations on the winter Choral performance.