Alexis is believed to have travelled to London from Northampton at 10.30pm on August 15.
Police are urgently seeking information on her whereabouts.
Alexis, who also goes by Lexi, is thought to have visited Leicester Square and Marble Arch, as well as Heathrow and the surrounding area.(Image: Met Police)
Her last known location was Tottenham Court Road on August 23.
Alexis is said to 5ft of slim build, with long, dark hair.
Detective Inspector Rory Wilkinson, from the Met’s missing persons unit, said: “We, and Alexis’ family, are becoming increasingly concerned for her welfare.
“Take a close look at the photo we are issuing today and if you recognise her, or have any information, contact us as a matter of urgency 101, quoting 1213/20AUG. If you see her, please dial 999 immediately and reference the same number.”
