I briefly liked the idea of taking or disabling the car (that would simple enough, just pull the coil wire or the ignition fuses). The trouble is, depending on how resourceful the A is, it is a simple matter to have the car towed and fixed, rent a car, buy a new car, call a cab, call a friend, what have you. So how effective this would be depends on the particular circumstances, whether the A would accept it. I think it might be worth a try to just ask her to not drive. Maybe take the car and give her cab vouchers? It depends so much on the actual circumstances. If Hayfmr divorces his AW and disengages, she will be free to do as she chooses anyway as soon as they are split, so anyone's ability to control this situation is, in the grand scheme of things, very limited.
As I am learning myself - the conventional wisdom is that all attempts to control the A's behavior are ultimately doomed to fail, and at best, only going to delay the inevitable.