I Am Heart Broken

Someone I love is on a downward spiral of drugs and alcohol. All because of three different ass holes. One guy almost gave her a std (she dodged a bullet on that one). Than a guy molested her and than a guy cheated on her (actually she was the other girl but didn't know about it). Now all she does is go out and drink and god knows what. I love her and I want to help her but she won't let me. I don't know what to do.