I think it's fine. In her work, in her magic fake universe, the actual origin of certain myths, legends and religions are different than the actual origin from our real world. She isn't writing a documentary or history book, it's a work of fiction.
If she was writing about real Native American mythology and said "actually, it was made up by white anti-magic people to tarnish wizards and witches" then yeah, that is a problem because that is incorrect and not something that should be in a book about facts, but saying that in her fake magic world with fake non-real character and secret hidden worlds then it's fine.
Like how in Persona/SMT gods and mythological creatures are all demons. Vishnu is a demon. Obviously that isn't true because it's a work of fiction that takes religious gods and angels and demons and other mythological creatures and just says "what if they are all real, but are demons? And you can even make them by mixing together a bunch of unrelated demons?"
I mean, yeah, I can see it sucking when a myth/legend that is part of your religion is included in something but changed by the author to fit their world but then again it's something that happens all the time in fiction. I mean isn't there a currently running TV show in America about Lucifer/Satan being a nightclub owner/playboy who also solves crimes? Like, that is glorifying and misrepresenting the personification of evil in Christianity. I'm sure some Christians have an issue with that but I think that the show-runners should be able to do that just like I think Rowling should be able to do this.
And I'm not saying "they do this to Christianity so stop complaining when they do it to something else" I'm just saying this sort of thing is super common and it's something I love about fiction. Seeing different authors and creators put their own spin on various well known (and not as well known) myths, legends and creatures. As a kid Disney's Hercules got me super into Greek and Roman myths and I love finding out about obscure myths and legendary creatures from games and then looking up the actual origins and the actual myths.