Kim Hazlett is understood to have caught a bus from Omagh to Derry on 27th May and was last seen in the Waterloo Place area of the city at around 3.40pm on that date.
Kim is described as around 5' 4" tall, slim with blue eyes, dyed black hair and a pale complexion. She has a pierced eyebrow and pierced lip.
When last seen she was wearing a grey hooded jacket, dark blue tracksuit bottoms and trainers.
Police would urge Kim or anyone who knows of her current whereabouts to get in touch with them at Strand Road police station by calling the new non-emergency number 101.