The incident took place at around 6pm on 26 January on B2036, Pound Hill North and involved a car hitting a 17-year-old girl.
She was taken to hospital and suffered life-changing injuries. She has since been discharged.
Police are trying to establish the full circumstances of the incident.
Witnesses or anyone with any information or footage is asked to contact Sussex Police online or call 101 quoting serial 1064 of 26/01.