State troopers responded to the scene, near the intersection of 161st Way and Smith Prairie Road near Yelm, at about 9:40 p.m. Thursday after receiving a report of a crash.
An investigation found that a 40-year-old Tenino woman was heading north on Smith Prairie Road in a 1994 Isuzu Trooper when she fell asleep at the wheel.
Her vehicle drifted into the oncoming lane and slammed head-on into a 1994 Isuzu Amigo that was heading south. The impact killed the driver of the Amigo, identified later as Linda H. Burkhardt, 55, of Puyallup.
The driver who fell asleep was injured in the crash. She was taken to St. Peters Hospital in Olympia for treatment and could be cited for a traffic infraction.
Alcohol and drugs were not a factor in the crash, the State Patrol reported.