French jewellery designer, nicknamed “the Coco Chanel of jewellery,” she was the director of jewellery at Cartier, and the lover and muse of Louis Cartier (grandson of founder Louis-François Cartier). Toussaint became known for crafting jewellery settings that were almost invisible, so as not to alter the precious stones that adorned them. Her famous La Pantheré (Panther) jewellery, worn by Wallace Simpson, Barbara Hutton, Maria Félix and Daisy Fellowes, became emblematic of the house of Cartier.
After moving to Paris in her youth, she first distinguished herself by decorating bags with embroidery, beads and chains. She met Louis Cartier on the eve of the First World War, when he was newly divorced. He hired her as head of the “bags, accessories and objects” department.
During the Occupation of Paris, in 1941, she displayed a jewel depicting a nightingale (in lapis lazuli, coral and sapphire) imprisoned in a cage (in gold) in the Cartier store window; she was arrested by the Gestapo, and asked about the meaning of the jewel and what she knew – “nothing” – about the whereabouts of Charles de Gaulle, who had taken refuge in London in the Cartier offices. She was released by the Gestapo, according to legend, by the intervention of her friend Coco Chanel. Meanwhile, Toussaint organized the transfer to Biarritz of the stock of jewellery left in deposit by customers.
She married Baron Pierre Hely d’Oissel in 1954, and thus became a baroness. He died in 1959. She retired from Cartier in 1970, and died on 7 May 1976 at age 89 in Paris.

Link to Wikipedia biography (French)