Ashleigh C. Williams, 21, of Port Orchard had been undergoing treatment at a Portland, Ore., hospital for critical injuries suffered in a car crash along Interstate 84 on the east end of Pendleton.
Oregon State Police said in a statement that Williams was driving east on I-84 in a Nissan Maxima on Monday morning when the car drifted toward the center median. She lost control as she tried to move back toward the traffic lanes, and the car crashed into a guardrail before coming to rest in a ditch.
Williams initially was taken by ambulance to St. Anthony Hospital in Pendleton, and then was airlifted to Oregon Health & Science University in Portland, where she died on Thursday.
Her brother, Jared Williams, 18, was transported to St. Anthony Hospital with minor injuries.
Oregon state troopers are continuing the investigation. Driver fatigue is a possible contributing factor, police said.