My best friend i have known her for 5yrs and now she has this boyfriend that i dont like he cheats,lies, ?

Takes her phone and he has told her that he hoped her and her kids would get run over by an 18 wheeler and has also said he wished her friends kids would die too but she keeps taken him bak and she don't ever call,text or hang out with any of us any more and she puts him before her three kids. We have tried talkin to her about him and she turns it on us and says our relationships are not no better so we have given up hope that she will give him up! Any suggestions on how we can get her to either leave him or to make her understand about him!