It happened before 9 am on the four-lane section of the highway.
The California Highway Patrol says the woman was eastbound when she veered off the road for an unknown reason.
Her car fell 200 to 250 feet down an embankment and caught fire. The victim was ejected from the vehicle.
First responders were able to put out the fire and help bring the woman back up the hill.
She was airlifted to a local hospital with major injuries. Officials say she was conscious and breathing.
The cause of the crash is still under investigation.