The incident happened near to the Furness and South Cumberland Supply Association building on Chapel Street, Egremont.
A Cumbria Police spokesman said: “The victim, a girl in her teens, was attacked by two young girls. She suffered injuries to her face.
“It is believed that a number of people were in the area at this time and may have witnessed the incident.”
Anyone with information is asked to call PC 2101 on 101 or call Crimestoppers anonymously on 0800 555 111 quoting log number 77 of the 21st September.