I would suggest putting an electric fence around the mare and also the stallion. Alot of stallions do not get along with other colts or gelding and will fight to the death. As for the mare, here you cannot put someone elses horse down unless you have pemission. Even if the horse is severly injured, a vet will not put it down unless they have permission from the owner.
I personaly would not breed that mare, because what she does to people, she will pass on to her foal and the foal will most likely do the same.
I would consider surrending the horse to some kind of spca and let them deal with her. I would stay far away from that mare, due to potential law suits...