Movies like Sibling Rivalry

Marjorie Turner is suffocating. Her younger sister Jeanine has no ambition, and her eight year marriage to Harry puts her in constant competition with his family (all doctors), of whom he is also competing for the affections. One day, she snaps while food shopping, and beds a mysterious man, who dies during the moment of passion. When she forgets her wallet, a vertical-blinds salesman finds it, and things get complicated from there.