Wanted: Dead or in Love by Kym Brunner

Impulsive high school senior Monroe Baker is on probation for a recent crime, but strives to stay out of trouble by working as a flapper at her father's Roaring 20's dinner show theater. When she cuts herself on one of the spent bullets from her father's gangster memorabilia collection, she unwittingly awakens Bonnie Parker's spirit, who begins speaking to Monroe from inside her head.

Later that evening, Monroe shows the slugs to Jack, a boy she meets at a party. He unknowingly becomes infected by Clyde, who soon commits a crime using Jack's body. The teens learn that they have less than twenty-four hours to ditch the criminals or they'll share their bodies with the deadly outlaws indefinitely.