The accident happened around 6:45 a.m. on Old Kennett Pike in Kennett Square.
Police say 18-year-old Kristen Felkowski of Wilmington, Delaware was driving a 2005 BMW in the westbound lanes of Old Kennett Road and approached a left curve in the road.
The BMW failed to negotiate the curve causing the vehicle to leave the roadway and stuck a tree.
Felkowski was pronounced dead at the scene.
The passenger, identified only as a 16-year-old from Scranton Pa., was taken to A.I. duPont Hospital in Delaware with non-life-threatening injuries.