Threaten to kill herself while trying to hold me hostage

I recently went NC/LC with my crazy mother. I waited for 3 weeks, staying at my friend's place until my step dad asked me to reconcile with her. I reluctantly accepted. Went in, we had some talks and not long until she started screaming at me for not listening to her (I'm 21). I made her admit that she treats everyone around her like slaves and the fact that she tried to prostitute her daughter. Knowing that she can't make me listen to her, she jumped me and tried to take my car keys, phone and purse. She said that she's the reason I have all these stuffs. She then gave me 2 options, 1 is to stay and 2 is to give her everything I have and I'm free to go. I had to call my step dad in. He explained to her that what she's doing is kidnapping (she's Vietnamese, her English is limited) and all of her answers were:" I don't care, I don't want to listen to you, I know what to do." Then she forced herself to hyperventilating, screaming like someone's torturing her, ran to the kitchen, held up a knife and threaten to kill herself. Needless to say, my two little brothers were traumatized. Before that, she threatened to kill me several times and the reason I haven't call the police on her is because of her immigration status (very complicated). My step dad is calming her down now and I'm still stuck here and don't know what to do.