Lexie Weightman, who also goes by the name Lexie Erin, was last seen at an address on Royal Street in Liverpool at around 11.30pm on Monday 17 April.
Officers have carried out extensive enquiries since she was last seen in Liverpool.
She is described as a white female, of slim build, 5ft 5in tall, with long straight blonde hair.
When last seen Lexie was wearing black pants and a pink top.
She is known to frequent the Liverpool area.
Anyone who has seen Lexie or knows of her whereabouts is asked to DM Merseyside Police Contact Centre or call 101.
