Looking for advice

Hello all, 
I am writing this because my sister was recently attacked by her ex boyfriend and I am looking for advice on how I can be there for her. A couple weeks ago, her ex boyfriend came to my dads house at 3am after he had been drinking because he told her he needed somewhere to stay. This is when he beat her, choked her, and tried to suffocate her telling her he was going to kill her. Both my dad and step mom were home but it is a very large house and they could not hear what was going on. Finally, at 6am she broke away and got downstairs in front of their door. My step mom heard a loud thud and that is when she went outside to see what was going on to find my sister laying there almost lifeless. Her ex ran and got in his car as my step mom chased after him but didn't catch him. After the police were contacted they said she is lucky to be alive. Since then, they have been going to court proceedings almost every week and he is trying to deny everything and say my sister is crazy. This is really taking a toll on her and we have found her drunk lying in her room by herself multiple times since this incident. I just don't know what I can do to help her. She is shutting everyone out and I don't want her to end up hurting herself. Please, any advice of what has helped some of you would be so greatly appreciated. I just don't want her to shut everyone out and become numb. She is also starting to regret following through with court proceedings and has been having panic attacks throughout the night.