The Landlady (1998)

In Sunshine, Nevada, the middle-aged housewife Melanie Leroy sees her husband Ralston Leroy shagging her neighbor and she freaks out. Then she poisons Ralston, who is allergic to seafood, in the dinner. Melanie travels to the California to the apartment building that she has inherited from her aunt and when she meets her tenant Patrick Forman, she believes that he would be a perfect husband for her. She uses her maiden name, Melanie Leroy, and becomes obsessed for him, killing anyone that might interpose between Patrick and her.