Authorities say the driver of the car, Christopher Blankenship, lost control of the car when approaching a curve on the winding road. The vehicle spun and rolled over at about 9:15 p.m.
Officer Kimberly Hemminger was partially ejected and pinned under the car. She was pronounced dead at the scene.
Blankenship and two other passengers in the vehicle suffered minor injuries.
Blankenship, a reserve officer with the Santa Paula Police Department, was arrested on suspicion of driving under the influence of alcohol and vehicular manslaughter. He has been placed on administrative leave.
Hemminger was a five-year veteran of the department.
The accident remains under investigation.