Sounds to me that the best way to avoid what appears to be an obvious plot hole would have been to avoid the time travel thing in the first place- then she gets to continue making millions without the plot hole. On the other hand, I've never read Rowling, so, in the future, I'll stick to ridiculing her idiotic views on American politics, and giving her my best regards and laughs when her countrymen gave her and others of her ilk the big fat one last June, and I'll back off of commenting on YA books that I haven't read, and will never read. Besides, even real fantasy authors like Martin, Bakker, and Abercrombie occasionally have some things in their books that don't always make perfect sense.