Okay, It is perfectly fine for authors to have seconds thoughts about stories they have written. It's natural and most of the time we all are unsure about things we do and say. Later WE ALL think "What if I would have done this different." We are humans, it's what we do.
My own personal opinion about the comment is - That's cool and honest for the "Awesome" (In my Book) J.K. Rowling to feel that way. However if it would have been different - that awesome scene in The Deathly Hollows Part 1 - You know, when Ron was having a mental fight with himself over killing the horcrux or Harry. When the horcrux showed him Harry and Hermione practically having sex in the smoke -all naked and shit- (Hot Scene by the way).
And maybe Harry Potter would not have been this successful (IDK) maybe it would have - because Harry Potter was pretty damn amazing. But I think it came out well, Harry and Hermione together would have been a distraction and maybe they would not have been able to fight off Voldemort because Harry and Hermione would have always been sneaking off to have sex or maybe make out - who knows. But the choice she made, the way she wrote it was amazing. It's better off as a suspense mystery book instead of a romance anyway.
You, J.K. Rowling deserve
Because you and your books and movies were awesome!!!!!!!!!!!
But I'm sure you already know that!