"Maybe I am, maybe I’m not. Care to find out?" She isn’t sure what Bellatrix wants from her. She isn’t sure if it’s a rhetorical question or a legitimate question. Getting it wrong leads to more pain. She has to be careful to do what Bellatrix wants or it leads to more pain. She wishes she didn’t cave to her torturer so quick but she can’t help it. She can’t stand the blinding pain of the cruciatus.