Warrior (Doppelganger)

Warrior (Doppelganger) by Brennan, Marie. mass_market edition. ISBN: 9780316027052.

When a witch is born, a doppelganger is created. For the witch to master her powers, the twin must be killed. But what happens when the doppelganger survives? Mirage, a bounty hunter, lives by her wits and lethal fighting skills. She always gets her mark. But her new mission will take her into the shadowy world of witches, where her strength may not be a match against powerful magic. Miryo is a witch who has just failed her initiation test. She now knows that there is someone in the world who looks like her, who is her: Mirage. To control her powers and become a full witch, Miryo has only one choice: to hunt the hunter and destroy her.