Uh, no one you know; she lives in Canada.
It has to be most painful for Rowling: That last chapter was one of the first she ever wrote. She knew right from the beginning that's where she wanted to leave Harry, but what she wants kind of doesn't matter anymore. Remember, Rowling didn't write Cursed Child -- it was written by some dude named Jack Thorne, which is probably why it reads like bad fan fiction. For real, not only is Snape resurrected just for the cheap drama of graphically killing him all over again, but at one point Harry literally explains that he's regained an ability he logically shouldn't have anymore just because the story requires it.
Arthur A. Levine Books
They couldn't even muster up an "a wizard did it."
It's said to be based on a Rowling story, but damned if I can find it, and I want you to look me in the eye and tell me Joanne ever wrote so much as a grocery list she didn't immediately post on Pottermore. I'm not saying they did this against her wishes, because she's clearly had more than a few hands in it, I just think she's resigned herself to taking a backseat in the $15 billion brand she created. That's because Rowling hasn't become George Lucas -- she's become Walt Disney.
For one thing, she's already got the theme parks, and yes, that's plural. We're not in Orlando anymore, Toto: They opened one in Japan two years ago and one in California this year, just a hop and a skip from Mouse Town, all with hundreds of Hogwarts Princess products available in their overpriced gift shops. But more than that, there's the infinite army of people it takes to sustain a global franchise like Disney or Harry Potter. Both are composed of dozens of movies, books, and video games at this point, and whatever Rowling might lack in variety she's more than made up for with an online portal of enough words of world-building to make George R.R. Martin puke. One person simply cannot keep all that going. At some point, you have to delegate. You hire artists, producers, and yes, even writers.