The crash happened at about 1:50 p.m. on the highway near Los Alamos Road.
Rosanne S. Webb, a 52-year-old Santa Rosa resident, was driving west in a blue Ford station wagon when she allegedly sideswiped a Jeep as she attempted to pass it, went into eastbound traffic and collided head on with a Toyota, police said.
Prior to the accident, witnesses had reported the station wagon was being driven recklessly, according to police.
Webb was killed in the crash.
Beverly J. Rick, a 77-year-old Santa Rosa resident and driver of the Toyota, was taken to a local hospital where she died a short time later, police said.
The driver of the Jeep was not injured in the crash.
All lanes of the highway were open by about 7:25 p.m., according to the California Highway Patrol.
The collision remains under investigation and anyone who witnessed the incident or the driving of the station wagon is asked to call accident investigator Perry Plattus at (707) 543-3636.