RCMP have yet to identify the woman, who they say was hit in the fast lane of Highway 1 while she was attempting cross the route on Tuesday night.
Officers say she and a second woman were suspects in a minor theft at a nearby store, and that both attempted to escape across the highway.
Emergency crews arrived at the scene at about 9:30 p.m. and the woman was taken to hospital with critical injuries.
Mounties haven't been able to find the second woman, but say they are hoping to speak with her to determine what happened prior to the incident.
Police say the driver of the vehicle stayed at the scene and is co-operating with investigators.