Courtney was last seen in the Southampton area on Tuesday, May 17, however officers say there is ‘a chance’ she could have travelled out of the city.
They are asking anyone with information to come forward to help in their search after carrying out their own enquiries.
A spokeswoman for Hampshire police said: ‘We have been carrying out enquiries to locate her since she was last seen, but we are now turning to the community for help.
‘It is possible she is still in the Southampton area but there is also a chance she may have travelled out of the city.
‘Please share our appeal and if you think you have seen Courtney since she went missing, or think you know where she might be, call us on 101 quoting 44220198492.’