Eibhlinn McAleer is described 173cm in height, of slim build with brown hair.
In an appeal on Facebook, the PSNI said she was wearing jeans, a three-quarter length blue anorak or jacket and wearing a woolly beret-style hat.
She was last on Upper Newtownards Road, Belfast, walking in the direction of Stormont.
Anyone with information as to her whereabouts or any sightings of her is asked to contact police immediately on 101 and quote police reference 1373 of 9/5/18.