Whispers are Begotten who hunger for secrets. The more the secret matters to the victim, and the more effort they put into concealing it, the more Satiety a Whisper can draw. The "objective" severity of a secret only matters insofar as it has consequences for the victim. The Whisper gains Satiety when the victim knows they've been found out, but strictly speaking, only the Beast has to know. In fact, some Beasts help protect what they've uncovered, if only so other Whispers can't uncover it, too.
At high levels of Satiety, a Whisper can only be satisfied by unraveling a vast conspiracy or digging up something supernaturally hidden. Exposing demons, vampires and mages may earn a large amount of Satiety, but it will not endear her to her kin. At lower levels, even the little white lies that pepper mortals' day-to-day lives are fair game: catching someone who called out sick to take a spa day, for instance, or publicizing someone's embarrassing fanfiction.