Hermione's Boggart

Yet another theory...

I know Hermione cares about her school work, but in every book, she's been willing to not only face expulsion, but to also face death to help her friends Harry and Ron. Why, then, would her greatest fear be failing everything when she believed that a crazy mass murderer was no the loose trying to kill one of her best friends? Keep in mind that earlier that year, Ron had woken up with Sirius Black standing over him with a knife and Harry had been risking his neak by sneeking out to Hogsmead. It's much more likely that she say one, or both, of them dead and lied about it later.