That's assuming she backs straight into the garage. She's come close to hitting my truck, and when I park I park virtually agains the wall. You can't walk between the truck and the wall. AND the garage is not small either.If you put a threaded anchor in the floor, you can attach removable chocks. A 2x4 is OK for many people, but a tapered wheel chock is better.
At one time I thought about mounting rollers so that when she hits them they force the car to glide into its spot. But then there's that issue again with stuff in the floor interfering with me moving 4X8 plywood panels around.