your SIL sounds like she's got serious issues. think about it: she's an asshole to you when she's sober, and then wants to fuck you when she's drunk. she's a manipulative bitch with self-esteem issues. she's obviously jealous of her sister, and she wants to worm her way into her sister's life. your SIL is not happy at home, so she wants what you and your wife have.
i'd be very careful with this one. this does not seem like a casual fuck. she wants much more than that...like breaking up your marriage.
