It is not a cause or even a barrier for the lady to think normally if she is under her enchantment. Even Brandon is concerned about what will happen after the enchantment gets removed because he has no idea how the curse and magic will terminate. He knew Casey was not an average human; he was a Meilleure, which meant he was even greater than vampires and werewolves, and it was not impossible for someone like her to kill him at any time, but in his view, this was one of the reasons he was hiding Casey from the truth and her destiny.