So I went and saw Rise of the Guardians, and I've had a couple ideas for other guardians. This was one of them.
Falling Star, or Stars, is an in-direct guardian. She is the first star of the night and the falling stars children wish upon. Every star in her body is a wish, and wishes are her center. She does not grant wishes, but she brings these wishes to the guardians that can fulfill them, making her a sort of messenger. I imagine she would be a much older guardian, and on regular speaking terms with the Man in the Moon.
Also, she's about eight feet tall. ^w^
Rise of the Guardians (c) Dreamworks Pictures