She is every bit as vile a bigot as Musk is, just with less (but still more than enough) money. And on top of that, her alter ego/pen name is male ("Robert Galbraith"), so it's yet another dose of bigotry on top - appearing as a male for... whatever reason, idk.
[1] https://www.advocate.com/news/jk-rowling-anti-trans-organiza...
JKR has probably received more of this abuse than any other woman. She's become a lightning rod for this deranged, abusive male behaviour, simply for advocating for women's sex-based rights and refusing to be intimidated to silence.