Just like the hanging magnet is pulling on the car, the car magnet is also pulling on the hanging apparatus. Unfortunately for the car, the apparatus is attached to it, so it all cancels out.
If your weight increased to 20x your current weight, without changing proportions, you would be about 2.7x your current height, width, and depth....just like OP's mum.
Just like the hanging magnet is pulling on the car, the car magnet is also pulling on the hanging apparatus. Unfortunately for the car, the apparatus is attached to it, so it all cancels out.