Acorna
She was just a little girl, with a tiny horn in the center of her forehead, funny-looking feet, beautiful silver hair, and several curious powers: the ability to purify air and water, make plants grow, and heal scars and broken bones. A trio of grizzled prospectors found her drifting in an escape pod amid the asteroids, adopted her, and took her to the bandit planet Kezdet, a place where no questions are asked and the girl might grow up free.

But Kezdet has its own dark secret. The prosperity of the planet is based on a hideous trade in child slave labor, administered by "The Piper" -- a mystery man with special plans for Acorna and her powers. But free little girls have a way of growing into freedom-loving young women, and Acorna has special plans all her own.
Fiction, Acorna (Fictitious character), Abandoned children, Unicorns, Child abuse
Anne McCaffrey, Margaret Ball, Margaret Ball
Margaret Elizabeth Ball is an American author of science fiction, fantasy, and historical novels. Under the pseudonym of Catherine Lyndell, she has also written romance. Ball has a B.A. in mathematics and a Ph.D. in linguistics from the University of Texas. A former Fulbright scholar and UCLA professor, she devotes her time to fabric arts and embeadery. - Wikipedia