Angel, aged 17, was first reported missing on July 14 and has links to Southampton, with Hampshire police sharing an appeal on behalf of Hertfordshire colleagues.
Originally from Hatfield, she was spotted on CCTV on July 22 at 7.26pm at Huntingdon railway station in Cambridgeshire.
She is approximately five-foot six-inches tall and very slim with blue eyes.
Since she was initially reported as missing, Angel has shaved her head.
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She is described as wearing an oversized red puffer jacket, navy tracksuit and black Fila trainers, and may also be carrying a yellow bag and a black rucksack.
Angel is known to have links to Southampton, Luton, Harlow and Hatfield, with police believing she is likely using the train network to travel.
Hertfordshire Detective Inspector Paul Chase said: “Our officers are carrying out numerous enquiries to find Angel, which is our top priority, as we grow increasingly concerned for her welfare.
“If you have seen Angel, or have any information that may help our enquiries, please make sure you contact the police immediately.
“Angel is not in any trouble – we just want to make sure she’s safe and okay.”
Police said that anyone who believes they are with Angel or has seen her in the “last few moments” should “call 999 immediately”.
