On m'a volé mon adolescence

In the 1960s, Evelyne, a 14-year-old teenager, reluctantly becomes her mother's confidante, who uses her as an excuse for romantic encounters with a work colleague. Evelyne finds this secret very difficult because she loves her father and her 12-year-old younger sister. One day, her mother leaves her husband and her two daughters. Evelyne, feeling guilty, tries to convince her to return home.