Jasmyn Chan died as she crossed a road with a group of friends in Sheffield on Friday evening.
Officers are investigating reports she was trying to help her younger friend get out of the path of the car when the crash happened.
Chief Inspector Stuart Walne, of South Yorkshire Police, said: "We have received a steady flow of information since Friday night and I have a team of officers working through the details to trace the car and, ultimately, the driver involved in the crash.
"I am certain it is just a matter of time until we catch this driver and can ascertain exactly what happened at 9.20pm on Friday night on Normanton Hill."
The officer added: "I am also renewing my request to the driver of this car to hand themselves in.
"Put yourself in the situation that Jasmyn's family and friends are now in."