The woman and the car's driver work for a Durham house cleaning service. They were on their way to a job when it happened.
The small caliber bullet came through an open window and hit the victim on the side of her head, just behind her ear.
The woman's injury was not life threatening. She was being treated at UNCH in Chapel Hill.
Investigators said they didn't think the shooting was an intentional act. They were checking homes in the area to see where the bullet might have come from.