It happened at about 2.45 pm on Saturday afternoon on the A76 new the junction with the C6N road towards Loch Ettrick.
She was the pedestrian who was involved in a collision with a grey Audi A6.
The girl suffered serious injuries and was taken by air ambulance to the Queen Elizabeth’s Children Hospital in Glasgow, where police say she remains in a stable condition.
The driver and occupants of the Audi were unhurt.
The road was closed until 10 pm that night to allow for a police investigation.
Sgt Jonathan Edgar said: “Our enquiries into this crash are continuing and I would ask anyone who saw what happened, and has not yet spoken to officers, to come forward.
“I would ask motorists using the A76 on Saturday afternoon and who may have been recording via dash cam devices to check their systems and provide any relevant footage to us as soon as possible.
“I’d like to thank those members of the public who stopped and assisted at the scene, along with our emergency service colleagues who attended the incident.”
Police can be contacted via the 101 number.