The girl and an 11-year-old boy were taken to Long Island Jewish Medical Center after Sunday's accident in Springfield Gardens.
The boy is in stable condition.
Police say it appears the 39-year-old driver of the vehicle had been in an argument with his girlfriend in the car when he lost control. The vehicle jumped a curb and struck the children at about 160th Street and North Conduit Avenue.
The driver stayed at the scene. Police don't believe he was drinking and no criminality is suspected at this time.
The accident remains under investigation.