The woman was driving her Mitsubishi Shogun towards Palmers Green, when she collided with an oncoming car and veered into Ironside Motors, a Nissan dealership.
Showroom manager Paul Bannister, who saw the car hurtling towards him from his office, described the scene as spectacular' and said it was lucky no one was seriously hurt.
He said: "The car hit a couple of cars parked on the road, went up the pavement and through the window which is half-an-inch thick the whole vehicle came in.
"It was very frightening. The building shook and the noise was unbelievable. It looked like something out of a movie.
"Glass was flying everywhere, but luckily it missed the salesmen and there were no customers."
A second salesmen in the showroom was slightly injured after being trapped between a desk and a wall, however he did not require hospital treatment. The driver of the Shogun was treated at the scene for shock by paramedics.