(((((Codeblue))))). I'm sorry, I know how hard this sort of thing can get, my big brother is still a witness.
I totally agree with what Mouthy said earlier-try to catch your sister in a love trap. I mean, when you think about it, she is as much a victim of that cult as any of us have been. When you're in the middle of it, it all looks so reasonable, then when you get out, it's hard to believe the garbage we all willingly ingested. Your sister is trying to save your soul in the only way she knows how, so try not to be too hard on her.
Maybe, with time, you can help her find her way out of this mess, so in the meantime, try not to lose your relationship with her completely. Hang in there, kiddo.