Mrs. Endicott's Splendid Adventure by Rhys Bowen
In 1938, Ellie is stunned when her husband, Lionel, tells her he is in love with someone else and wants a divorce. With their two sons grown, Lionel expects that Ellie will move out of their home and into a small cottage in the village or move to London. Ellie instead decides to travel to France with Mavis, her former housekeeper, and Dora, an older woman that she's known for many years. With the South of France as their destination, the trio end up in Saint-Benet, a small fishing village near Marseille.