Brooke is a naiad, a water nymph. She appears in The Demigod Diaries and inhabitants a brook, hence the name.
Appearance
Brooke is a pretty naiad, like most of them. Pretty in a naiadish way. She has green hair that's sort of stringy. Her skin is pale. Her lips are blue, like a drowning victims'. She wears a blue dress or slip.
The Demigod Diaries
Brooke appeared here when Piper, Leo, and Jason are looking for Buford. She warns them about her "crazy cousins", and then vanishes.