Love Songs (2007) on Netflix

Plot summary

Julie Pommeraye and Ismaël Bénoliel live together in Paris. Julie is uneasy about the hours Ismaël passes with Alice, a colleague of his, so she asks Alice to join the two of them. The three walk through Paris, go out, read and sleep together; some nights are light, others bring jealousies. Julie tells her older sister Jeanne and later her mother about the arrangement. One night Julie complains that Ismaël and Alice have grown close. Ismaël calls her jealousy strange when she too sleeps with Alice, and Alice says she is there to bring the couple together.