The crash happened just before 7 pm Wednesday.
Police say Rosa De Sousa was crossing the street at Winton Way and Fay Drive.
A white Ford pickup truck traveling north on Winton hit her and drove away from the scene.
The collision sent De Sousa into southbound lanes of traffic, where she was struck by another vehicle.
The driver of that car stayed at the scene.
If you've seen the Ford pickup truck involved in the hit-and-run, call Atwater police.