Officers with the Bullhead City police department traffic bureau do not yet know why Marissa Leeann Kirkling, 23, lost control of her vehicle as it traveled down North Oatman Road.
The accident took place between the Bullhead Parkway and Arcadia Drive, shortly after 12:30 p.m..
Neither Kirkling nor her passenger, whose name has not been released, were wearing their seat belts at the time of the accident.
A police department spokesperson said the driver was sitting on top of a fastened seat belt rather than having it properly secured around her body.
Kirkling was flown to University Medical Center in Las Vegas. Her passenger was treated at the scene by paramedics.
The accident remains under investigation.