Wikipedia had her at £600 million in 2016, so probably not a billionaire, but that's quibbling. I honestly don't think she did anything wrong, but I also think she got that rich because she wrote her books in a world built on exploitive systems. How much less would she have if every book shop employee, amazon employee, or factory worker in china making harry potter ephemera was paid fairly for their labour?

More importantly, if she only had £60 million would she be any less happy?