Beneath My Skin by Brea Viragh

Strong-willed Mariella Revely has been involved in the supernatural world since she was six years old, when the strange demon script first appeared on her skin after the car crash that killed her mother. Nevertheless, she’s managed to live a relatively normal life among other humans. It wasn’t until she knocked—literally—into the handsome djinn Dax Parker that her life finally began to fall apart.
Sometimes it takes accidentally interfering with the wrong hit job, a little faith, and a guardian demon to come out on the right side of treachery. Can Mariella trust the roguish, captivating djinn? Or is she better off sticking with the demon she knows?