Echo in Emerald.
(Book)

A Misfit and a Mystery In the royal city of Camarria, a street urchin named Chessie lives by her wits, always attended by her two faithful friends, Red and Scar. What no one realizes is that the "friends" are really echoes, creatures who look exactly like their originals but who possess no volition of their own. Echoes normally are only born to high nobles, and Chessie doesn't want anyone to start asking questions about her past. So she's developed the ability to move between bodies so rapidly that she can maintain the illusion that she and Red and Scar are three separate people. After someone tries to murder the crown prince, Chessie gets entangled in the investigation when she comes to the aid of Lord Dezmen, the high noble who's trying to solve the crime. From the back alleys of Camarria to a society party to a rural province, they track down clues.Until one of those clues leads right back to Chessie.