Death of the Author doesn’t really work when the author is still alive, profiting off the work, and gets to decide which new projects get an official stamp of approval. Plus, she’s absolutely delusional enough to believe that her continued royalties off the franchise justify her views and that people must secretly agree with her.
There’s enough other great works out there to put your time and effort into building an expanded world around, if that’s your thing, written by authors who are far kinder and more talented than Rowling. Might I suggest Ursula LeGuin or Terry Pratchett for some light and enjoyable fantasy?