The Seward County Sheriff's Office says the westbound car crossed the median and the eastbound lanes, and kept going until it struck the bottom of an embankment.
The Sheriff's Office says the driver, 29-year-old Nell (Renee) Jorgensen, was flown to a Lincoln hospital where she died. Her daughter, 11-year-old Morgan Smith, was pronounced at the scene.
Jorgensen's 4-year-old son also was in the car. He was treated for minor injuries.
They were from Hannibal, Missouri, and had been headed to a family reunion in Wyoming.