Bellatrix turned out to be the weaker of them both; she knew this just as well as she knew her own body, knew Hermione’s, and though it pained some insignificant portion of her mind to find herself beneath the witch, it was still a well-earned position. Whatever Hermione had been before the switch and the subsequent breaking of her mind, she was  that  no longer. But she  was  assertive, dominant, strong enough to bind up new purpose beneath her raw form.