My sister is psycho!! Opinions please?

Ok I would like honest answers. My sister is seriously psycho, if things don't go her way she will start talking so much **** and doing so many things to purposefully hurt you. Tonight was like the straw that broke the camels back. She gets more psycho like this when she drinks. She is 32 years old and I am 29. So I gave in and was trying to be nice and go out with her for her birthday, dancing and drinks. I try not to drink with her normally because she acts psychotic whenever she drinks, very controlling and wants things her way or she'll start demanding and getting loud and spiteful. So tonight we went dancing and drinking, we were out for about an hour and I talked to my ex boyfriend we broke up 7 months ago (we've just became friends again) even though I have a boyfriend. My boyfriend is far away so I don't see him. I admit, I did once hook up (not sex) with my ex while I was with my boyfriend that I never see. But I know for a fact I never want to again. I told my boyfriend when it happened because I felt horrible. But I can't deny it, I never see or talk to my boyfriend , and my ex was like my best friend and one person I feel completely comfortably talking to. I have no other friends. Talking to my boyfriend is limited and I can't even call him and am only able to see him once a week. So tonight, I wanted to go chill with my ex for a bit and leave the dance floor. I told her we were going to leave in an hour. She started flipping out and getting angry, and asking me questions, what you're not going to dance? You want to leave? You're not going to hang out with me? And I said yes, I am but I'd like to leave in an hour. So she said ok, I'm going to call my friend and see if he wants to hang out. By no means did I want to stay at the club for a long time. It's not really my scene. So she called some guy (I'm sorry but she sleeps with any guy who will give her the time of day) and invited him to the club, started disgustingly hooking up with him (kissing/making out) on the dance floor. When I saw that I told her I wanted to leave, she seemed fine with it then, I guess because she had a guy to keep her company, and I told her when she wants to come home, to call me and I'll open the door. So, I leave, meet up with Aaron (my ex) and then 15 minutes later, she calls me and says the guy is dropping her off because he doesn't have his own place, to go have sex. I told her where I was so he could drop off there and then we would drive home. So they get there and are making out for like 10 minutes in the car, way gross, and then she gets out of the car and just starts bashing Aaron and I. She tells Aaron the party he went to last night seemed a bit gay and lame. Started saying how our state and city sucks and hers is a lot better (she lives in NYC), stating how she hates her family and that we are so selfish and stuck up, that she hates our mother, that she never wants to talk to us again, then she says she's going to call my boyfriend and tell him I'm cheating on him and I am hanging out with Aaron (my ex), that I'm crazy because I stab myself (I had a past history with cutting and attempting suicide), and she was making negative comments that I have issues because I like to stab myself and I want to kill myself by overdosing on pills, cutting myself and such. She just kept going on and on, bashing me, my family, and Aaron. I was in shock, then we were driving home I told her, her behavior is inappropriate and she gets more mad and telling me I'm a horrible person for hanging out with my ex, that she's going to call my boyfriend and tell him all this horrible **** about me and that I am a cheater (I am not, I made one mistake and admitted it), that she hopes one I day I do kill myself, and that she doesn't give a **** about me. This is someone who I've bent over backwards to be there for her. How should I handle this, I don't want her ruining my relationship with my boyfriend of 4 months, I don't want her ruining my relationships with my new friends or people I know. She is an embarrassment and I am scared of the damage she can cause because of her psychoness. What do you think, how should I handle this?