Shannon Heald was last seen in Kirkham town centre at around 6.20pm yesterday.
She was wearing a long black jacket with fur on the hood, a black top, jeans and black and white Nike Harachi trainers.
She is around 5ft 3 inches tall.
She has links to Morecambe, Lancaster, Kirkham and Preston.
Sgt Dan Whitaker said: “If you have seen Shannon or know where she is, please get in touch with us as soon as possible.
“Shannon – if you are reading this, please make contact and let us know you are okay.”
Anyone with information should call 101 quoting log number 1266 of February 18.