The incident was reported shortly before 12:30 a.m. on the transition road from the northbound 57 Freeway to the eastbound 60 Freeway, a California Highway Patrol spokesperson said.
Investigators believe the unidentified victim got out of her vehicle following the first collision and was then hit by a passing car, which did not stop. She was pronounced dead at the scene.
The occupants of the second vehicle involved in the initial crash were not injured.