Ronnie Quinlan was reported missing from Birchington at around 8.40pm on Wednesday 14 July 2021.
It is thought she may have since travelled by train to the Gravesend area or London.
The 14-year-old is described as being around five feet, seven inches tall, with straight, long blonde hair. She was last seen wearing black jeans and a pink sleeveless top which has ruffled shoulders.
Anyone with information is asked to call Kent Police on 101 quoting 14-1408.