Before Paco Rabanne, Paris, October 2015.
Celine backless sweater + gently flared pants. 
Recreate her look (kind of):
Backless sweater: Sonia Rykiel sweater,  Preen backless sweater, or Vince mixed media open back sweater
Agnona stretch-wool flared pants,  Chloe stretch-wool flared pants, Topshop Flared trousers, ASOS Flare pant with button front, Theory Stretch-crepe bootcut pants, Gucci wool skinny flare pants or Alexander Wang twill flared pants