Thanks guys!
It is kinda tough, because I have conflicting feelings, pulling in opposite directions, and she is my sister, and I'm sure she's very well meaning, and has a good heart; but she's just so misguided and clueless at times, and seems incapable of taking responsability for her life and actions.
I don't even want to think too much about her, it's her life; I want and need to just focus on my own life, creating my own heaven on earth.
The incident with the machete, I only found out about a few months ago; my mom knew and told me, but also said that my sis had told my mom not to tell me. It's all the secrecy and lies and deception, that seem central to her life story. There's not so much complete total honesty.
So yeah, she's taken him back; he's bought her a new car, they have a new dog too (they have 2 now), it's like he's bought his way back in to her life. I also think, it's all making her more dependent on him. It's all so much BS and lies.
Other conciderations are that I have a little neice; and also there's my mom, who's getting on in years now..
Thanks once again for all your comments.