State police say the girl was on Interstate 495 north in Merrimac just after noon on Sunday when she was shot. She and her family were returning from Massachusetts to their home in Limington, Maine.
The girl was taken to a hospital in Newburyport with injuries to her upper arm. Her name was not made public.
A state police spokesman said Monday that the girl was released from the hospital and was recovering at home in Maine on Monday.
Police said the shot was fired by a male passenger in a white Honda Accord with tinted windows with possibly Massachusetts registration plates.
Witnesses say there had previously been some sort of highway dispute between occupants of the two vehicles.
(Copyright 2012 by The Associated Press. All Rights Reserved.)