The Mistress (1999)

Alex is the English teacher of Michelle, the mistress of the rich businessman Henry. In the beginning she scorns their relationship believing that it is based on money and is demeaning to women but nonetheless she gradually forms a friendship with Michelle. As her sexual imagination begins to grow she falls under the allure of Henry and after she is seduced, she takes Michelle's place and becomes his mistress. The second half of the movie charts her downfall in the role of the mistress.