The 15-year-old was last seen on Wednesday 18 August.
Police would like to find her to make sure she is OK.
Atlanta is about 5ft 1ins and was last known to be wearing a black jacket and light grey trainers.
She has links to Kelvedon, Ipswich, Chelmsford, Maldon and Stratford.
If you see her or know where she is, please call Police immediately on 101.