Shay, 15, was last seen by her family around 12pm on Sunday 1 August and they are extremely concerned for her welfare.
When she left her home, Shay was seen walking in the direction of Denmead Village, but officers believe she has travelled to the Farnborough area. Shay may have also have gone to the Lewisham area in South East London.
Shay is described as being white, around 5ft 2 ins tall, of medium build and with dark hair down to just below her shoulders, and has a nose piercing on both sides.
When she was last seen, she was wearing charcoal coloured jeans, a white hoodie and black trainers. She also had a striped beige, red and blue shoulder bag.
If you have any information about her whereabouts please call 101, quoting the reference 44210305969.