J.K. Rowling's Favorite Word?

We've been working our way through Harry Potter and the Half-Blood Prince a chapter a night, sometimes two. I've been the reader and can't help but notice one word that appears more than any other, besides character or place names: incredulously.

Harry, Ron, and Hermione are continually looking or shaking their head "incredulously."

There has to be some other synonyms Rowling could have applied. She could have dropped the modifier in scenes where [so-and-so] dropped his/her head and shook it incredulously. This is a case of overdoing it. Then again, her primary audience is children, who often require the extra description—although, I doubt most of them even know what the word means or how to say it.