The Forgotten Beasts of Eld by Patricia A. McKillip
Sixteen when a baby is brought to her to raise, Sybel has grown up on Eld Mountain. Her only playmates are the creatures of a fantastic menagerie called there by wizardry. Sybel has cared nothing for humans, until the baby awakens emotions previously unknown to her. And when Coren - the man who brought this child - returns, Sybel's world is again turned upside down.