How do I deal with my horrible sister in law?

For years now this has been bugging me. She is an incredibly miserable human being. From the moment I met her I felt that she has needed psycho therapy. Her temper is that of a 4-year-old child, she's a pathological liar, an adulteress, a child abuser, and has "whipped" my brother beyond belief. I thought he was stronger than that. She guilted him into the relationship in the first place and pretended to be pregnant to get him to marry her. On top of all of this, she treats my mother like crap and when anyone says a word she threatens that no one will see my brother or her kids again. She dresses like a complete hoe at family events (which is outright disrespect of my dad) and usually ruins them with one of her temper tantrums. I am finally standing up and refusing to deal with her bs anymore. Enough is enough already! This is hurting my whole family. The only reason anyone in my family has dealt with her for so long is so that they don't have to deal with even more temper tantrums and degrading behavior. So, there are kids involved and she is even talking bad about me to her oldest kid (how adult is that?) The family rejoiced when she said she won't be at the holidays this year, but what about next year? I wish my family would quit being spineless and let her know that she has behaved unacceptably. Instead, they just say it behind her back. I think she needs to hear it all. I have never had such a hatred for one human being in all my life. I am tired of thinking about it and being asked about it but it has to be dealt with somehow.