What horror movie is about the new girl in town who becomes obsessed with that one guy.?

Okay, a girl moves to town and becomes obsessed with this one guy. I'm pretty sure he doesn't want to have an affair, so the chick starts killing random people, like the guy across the street who saw her digging up something or something like that? Maybe he was keeping a lookout or something. Anyways, at the end of the movie, she ends up dieing because the guys wife runs her over with her car multiple times. What's the name of this movie?