The most likely explanation to me seems that she's one of those "hillbilly" types. I don't think she was just a crazy person either. So what is Jenifer exactly? I wouldn't call her a zombie, because she seems very much alive to me. It was entertaining, and that's all I'm worried about. Some parts of it are silly, yes, but I don't care. And why doesn't Frank kill her in the seclusion of their little shack, instead of outside where he's sure to be stopped? It seems to be a never-ending cycle, with Jenifer simply finding new men to seduce into keeping her dirty little secret. A police officer refusing to go to the police after folks are murdered in his house, for instance. Or at least, things that make the story a little bit silly. He's thwarted by a local hunter, who kills Frank and starts the cycle all over again. So he takes her outside, ties her to a tree, and plans to behead her. He gets a job at a local grocery store, leaving Jenifer alone to eat some more people. Instead of going to his colleagues, the police, he buries the bodies and goes on the run with Jenifer. Having had enough, Frank hires a carny to kill her but that man ends up stuffed in Frank's refrigerator. She starts off by eating his pet cat, and then escalates to the little girl next door. Frank soon realizes that Jenifer isn't just a helpless little victim. I guess you could possibly put this in the torture porn category, because it features sex that is so disturbing that it's hot (for me at least, but maybe I'm just a freak).
After being raped by her in his car, they begin a strange little love affair. But Jenifer is quite the little seductress, and Frank absolutely cannot resist her. His wife isn't happy about it, especially after a brutal make-out session with Jenifer, and she leaves him.
So he has her released from the facility and takes her home. But Frank doesn't like it, because he sees her as merely a victim. She can't speak or communicate in any way and, since the police force believes her to be mentally handicapped, she is sent to a mental facility. Her face is deformed, but she is otherwise quite attractive (what we call a butter-face). We first meet her when a police officer, Frank (that guy from "Wings" I can never remember his name), saves her from being butchered by a homeless man. In this episode of Masters of Horror, we meet Jenifer, a strange but somehow lovely young lady.