She's mentioned in at least three chapters. In chapter 12 Quirrell describes her as the "quote undying unquote Baba Yaga". (To my knowledge she's not mentioned at all by Rowling.) The Law of Conservation of Detail tells us that she is going to be plot-relevant somehow.
She appears in the Prisoner of Azkaban video game.
New chapter!
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 102.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: