I'm just waiting for the other shoe to drop. As we already know about their daughter so something going to happen like the sister ressurcts her imouto due to a loop hole or this is just a set up to make her confess her feelings for her best friend/ keep her as a girl to dress her up in outfits.
The author made the mistake of making her very very hateable, there's no coming back from that. Not even in a funny "haha, it was all a trick" way. Event the chapter title is telling us that.
Okay I don't get why she/he is so hung up on the emotions disappearing when in all likelihood they are just as much a part of the sisters fucked up game as everything else was at the end of the day.