Police say it happened Sept. 14 at about 1:55 p.m., when a woman driving a vehicle accidentally cut off another driver.
The suspect who had been cut off then followed the victim to a Bank of Montreal drive-thru at 99 Boulevard de l'Hôpital, got out of her vehicle and walked up to the victim's vehicle.
The suspect then grabbed the victim's hair and slammed her head against the steering wheel, police say.
The suspect was driving a light green Toyota Tercel made around 1996, with a man and at least one child also in the car.
She's described as a white, French-speaking woman, 25 to 30 years old, standing about five feet six inches tall and weighing about 180 pounds. She has brown hair, brown eyes and a piercing on her lower lip.
Anyone with information is asked to call Det.-Sgt. Kelly Lacroix at 819-243-2345, ext. 1330.