For one thing, she's almost asleep when she says that, and for another, I would think that wielding that kind of power, causing that kind of damage among your enemies would indeed make one somewhat exhilarated. No different from the kind of aggressive self-congratulatory language you often hear from warriors in movies and the like (I won't claim to know if they do it in real life as well, I should think so). The rest of that paragraph puts it all in perspective.