friend in an abusive relationship?

[Jacob Black supporter]

my friend called me yesterday. she told me that her boyfriend is dangerous. Now i've met him and he of course seemed perfectly normal. he was funny, nice and good looking. of course her boyfriend told my best friend that his mom was crazy and don't listen to her when she tells her things. so my friend believed this. but now she knows that he is dangerous. he also needs psychological help because he dreams peacefully to him killing others, and he told my friend that he can sleep to those movies as long as he is thinking about killing people he doesnt like.

like her mom. my friend is scared because he said if she ever leaves him, the next guy she is with he will kill them and torture her. and if she cheats on him, he will kill her. she told me not to tell anyone, but im really scared for her. i dont know who i can tell if i told have solid evidence. and if she refuses to get out of the relationship, or tell anyone, is there anything i can do?