She sounds like a really nasty manipulative person. I can't believe she'd laugh at you (well, of course I do believe it, there are some really crooked people out there.) She just seems so poisonous, so toxic... She's making you relive the abuse as though she was getting something out of it. And quizzing the bloody rapist about all the salient details is just vile. I'm sorry to have to say it, but your sister is filthy. I really hope you're able to get out of this situation some time. It's just awful reading about it, I can't imagine living it.
Stay strong, and remember, you're not accountable to her. She has no right to persecute you in this way.