The matriarch of her most famous book proclaims "We never marry in our family," although her granddaughter eventually marries the cultured Gaston.  
This author introduced the principle that if you can tell the color of a woman's hair, she's not wearing a chic enough hat, in her story "The Salesman."  In one of her novels, Alain leaves Camille after the she pushes his cat Saha off a balcony.  A sequel by her sees its title character commit suicide in front of his old photos after The Pal leaves town; the preceding novel began with its protagonists fighting over a pearl necklace before seeing 18-year-old (*) Edmée marries Fred Peloux, infuriating Léa.  The matriarch of her most famous book proclaims "We never marry in our family," although her granddaughter eventually marries the cultured Gaston.  For 10 points, name this author who chronicled the Parisian demi-monde in the Claudine novels, as well as in Chéri and Gigi. 
This author introduced the principle that if you can tell the color of a woman's hair, she's not wearing a chic enough hat, in her story "The Salesman."  
Sidonie-Gabrielle {Colette}