It happened just before 9 a.m. in the 2800 block of Orange Grove Road, about one mile southwest of Interstate 40 and Rivins Lake near Hillsborough.
Troopers say the mother, 35-year-old Cherylann Smith of Efland, was distracted before losing control of her Chevy Suburban.
Smith told troopers in a statement that she looked down briefly to find some McDonald's coupons.
A witness told ABC11 Eyewitness News he was in his driveway at 8:40 a.m. when he saw what happened.
"[The] SUV came off the road, into my driveway, swerved, overcorrected, overturned and then fell next to the creek down there into the ditch," Gilbert Baumann explained.
The Highway Patrol confirmed that's what happened.
Troopers say the SUV carrying Smith and her five children flipped once and landed upright.
"There were five kids in the truck, SUV, three of whom were crying outside, running around, 'call daddy, call daddy,'" Baumann said. "The mother was helping the little 6-year-old girl."
The rear driver's side portion of the roof was crushed, killing Scottlyn.
"The girl was totally full of blood and was not moving, but they said the girl was still breathing and eventually the girl stopped breathing," he added.
The other children in the car, 3-year-old Cheyanna Smith, 4-year-old Lorelai Smith, 8-year-old Jacob Smith and 9-year-old Caitlyn Smith were not injured but transported to Duke Hospital as a precaution.
The Highway Patrol says all of the children were properly secured in car seats or seat belts.