The Washington State Patrol reported the death on Sunday.
The child was identified in an accident memo as Isabella Rose Bednarski. She died Friday, troopers said.
The two-car collision occurred around 3:20 p.m. Monday on Highway 522 east of Fales Road.
It killed a Redmond couple, Stanley and Joan Kinger, 79 and 76. They were in a Ford Fusion.
The child was a passenger in a Mitsubishi driven by a Monroe man, 24. He remains at Harborview Medical Center in Seattle.
Troopers believe that the driver of the Mitsubishi was heading east and crossed over onto the westbound shoulder. The Mitsubishi hit a traffic barrel that was in some grass beyond the shoulder. The driver overcorrected before crashing head-on into the other car, troopers said.
More Local News Headlines
Fireworks danger rises with heat Lawmakers OK 11.9-cent gas tax hike in transportation package $385K settlement reached in deadly Broadway crash Project Homeless Connect unites people with services Monroe mayor and City Council members are getting pay hikes Lynnwood council candidates stress importance of community Tulalip fire death blamed on outdoor burning that spread 1:46 p.m. Stanwood-area home destroyed by fire, no one hurt 1:09 p.m.
Our new comment system is not supported in IE 7. Please upgrade your browser here.