The Life and Loves of a She-Devil (1986)

Ruth has everything. A large, warty body, a standard house in the suburbs, two whiney children, a dog, a cat and a guinea pig. She also has Bobo, her unfaithful accountant husband who resents her very existence. Bobo wants, and is wanted by, Mary Fisher. Mary Fisher lives in a lighthouse by the sea and writes about love. When Bobo leaves Ruth for the novelist, she decides that Mary Fisher doesn't know the first thing about love. Ruth intends to teach her.