The Delaware State Police says it happened Friday afternoon on Conaway Road north of Phillips Hall Road.
Troopers say 21-year-old Dakota Price of Laurel, Del., was driving westbound on Phillips Hall Road when for unknown reasons he traveled off the right side of the roadway into an open field.
Price then re-entered onto Conaway Road and struck a minivan driven by 59-year-old Janice Adams of Pittsville, Md.
Adams died at the scene. Her two passengers, 64-year-old Patrick Adams and 16-year-old Madelyn Riekert, were taken to hospitals.
Riekert is being treated for serious injuries. Patrick Adams was released after being treated for minor injuries.
Delaware State Police are continuing to investigate. There are no charges at this time.