The Becoming — Lynne Ewing

VANESSA, Serena, Jimena, Catty, and Tianna are five seemingly ordinary girls from Los Angeles. But the truth is that they are all far from ordinary. They each have a secret power that separates them from others--and makes them DAUGHTERS OF THE MOON

Lately, Tianna has been feeling unsettled, and she can't understand why--she has a great boyfriend, good friends, and, for once, a loving foster home. But still, she can't shake the thought that something, or someone, is after her. At a skateboarding competition she runs into two of her most feared enemies, Justin and Mason. Only now, they claim they've come to help Tianna--to warn her of her becoming. She has no idea what they mean, but deep down, Tianna senses herself changing. She knows that every Daughter has a dark side, but is hers threatening to overtake her?