My kids step mom emotionally abuses them...?

she calls them fat azz and all kinds of names ...she beats up on their dad in front of them and she has even pulled knives on their dad in front of them ..their dad is starting to be just like her...the court raised his child support and he told my kids he didnt want to see them anymore and that they werent getting any christmas from him because i was an evil bi@#$.....i dont allow my kids to see him very often because of her and his behavior....his wife talks to people that arent there, she tells my kids that her father is in the mafia and is going to come and kill us all,she pulled a knife on their dad in front of them and said her secret service agent cousin told her to kill him...and numerous other incindences...she also claims to be a witch and have special powers.....what can be done to get this woman commited ?she is nuts and i will not allow my kids around her ever again...