Things Shauna says to Jeff during/after sex while cheating on Jackie

There’s no doubt that Shauna suffered trauma while causing Jackie’s death, but she was a strange duck before the plane crash. In episode one, she asks Jeff to tell her that he loves her during sex (he didn’t want to), and she says she’ll turn their baby into a killing machine if he comes in her. Shauna has always been aggressive and never remotely likable. She didn’t have any problem getting in Tai’s face at the party the night before they boarded the plane. Could the killing machine comment be foreshadowing? How could any child of Shauna and Jeff turn out good?