Courtney was last seen in Doncaster on the afternoon of Saturday 22 September 2018.
It is believed Courtney, who is with a man aged in his twenties, was in Harrogate on the night of 22 September and then moved on to York on 23 September 2018.
Courtney is described as white and having light brown / ginger shoulder length hair, which she usually wears down. She is of slim build and has brown eyes. Courtney was last seen wearing black Nike trainers, dark skinny jeans and a jumper.
Officers are concerned for Courtney’s welfare and urge anyone who may have seen her in the York area to get in touch. Dial 101, press1 and pass information on to the force control room.