Police are concerned for her safety and urgently want to hear from anyone who has seen her.
Police say that Millie was last seen in the Southwell area at around 03:30 on Monday 22nd May 2023.
She is described as 5 feet 2 inches tall, medium build with brown hair.
Millie was last seen wearing a black T-shirt, black legging and white Fila trainers.
Millie is believed to be with another missing child, Sabina.
If you have seen Millie or have any information on where she is, please call us on 101 quoting incident 726 of Sunday 21st May 2023.