Killing Me Softly Adam Raped His Sister The Movie" Killing Me Softly" ... By Heather Graham?

The movie" killing me softly" ... by heather graham? - killing me softly adam raped his sister

I just saw this movie .... It's nice, but do not understand, why Adam killed his sister, women had? I mean, it is not your sister, right? Why break with Adam and Alice at the end of the movie? Is it because they do not trust him?