My sister, whom I love dearly, is on a downward spiral. She has threatened to kill herself over and over for attention, and I try to giving loving, stable support for independence. I've been her main (and often, only) person to reach out to in times of trouble and have been able to calm her down when she was unable to see her bf's point of view in fights. 

Recently, my sister freaked out over her relationship coming to an end. She lied to him about everything: her age, her NAME, her past, and no longer works. She has been using him for money and is on a downward spiral. He tried being there for her, but when he took a weekend visit to his family's home for Thanksgiving, she was unable to rebound thinking he abandoned her. She's placed all the blame on me because I was the one to give her advice through all of this. She's very destructive and I want to give her space to figure this out. She's emailing me and trying to ruin my relationships and it's tearing me apart. I don't know what to do. Can someone advise? I don't want to lose my sister, but she WONT seek help. How can I support her while she's a tornado all around us?

tl;dr: My sister is a tornado in relationships and I'm trying to lesson the wake of her force so no one is further hurt, but it's too much for me now.