Ava was last seen in the Woodhouse area at around 3pm on Thursday 29 July.
She has not been seen or heard from since and her family and officers are growing concerned for her welfare.
She is described as mixed-race, around 5ft 9ins with a medium build and dark hair.
Have you seen Ava?
If you think you know where she might be, please call 101 quoting incident number 938 of 29 July.