Everyone knows Édouard Manet and Berthe Morisot, but Julie Manet, not so much. She was Édouard’s niece—the daughter of his younger brother, Eugène Manet, and Morisot. A pretty girl growing up in a circle that included Degas, Renoir, Monet, and Sisley, Julie served as a dark-haired muse to these artists. When she was 10, she began a diary later published as Growing Up With the Impressionists, full of valuable insights on the French painters. Julie’s father died in 1891 and her mother followed him in 1895. Julie, 16, went to live with her cousins. She married Henri Rouart’s son, Ernest, lived out her days as a devout Christian, and amassed an impressive collection of paintings. In this exhibition on the mysterious, beautiful Julie—the first ever—portraits, works from her collection, and other relics from her life are on view. —E.C.