|Les Biches (The Does; Bad Girls; Girlfriends) (1968) [Frederique]: Stabbed in the back by Jacqueline Sassard while Stephane is standing in front of her make-up mirror.
The Discreet Charm of the Bourgeoisie (La Charme discret de la bourgeoisie) (1972) [Alice Senechal]: Machine-gunned, along with the rest of her friends, by a group of revolutionaries who invade their dinner party. This turns out to be a dream sequence, but then, so does everything else in the movie.
And Then There Were None (Ten Little Indians) (1974) [Ilona Morgan]: Bitten by a poisonous snake (off-screen) that Richard Attenborough had planted in her bathroom; we only see her walk into the bathroom, and her body is shown afterwards when the others discover her. (Thanks to PortsGuy)
Coup de Torchon (Clean Slate) (1981) [Huguette Cordier]: Shot in the chest by Isabelle Huppert after Stephane angrily chases Isabelle into her bedroom; we only see Stephane's back during the shooting.
Mortelle Randonee (Deadly Circuit; Deadly Run) (1983) [The Grey Lady]: Shot to death by Isabelle Adjani. (Thanks to Yani)
Faceless (Les Predateurs de la nuit) (1988) [Mrs. Sherman]: Stabbed in the eye with a hypodermic needle by Brigitte Lahaie in Stephane's hospital room. (Thanks to Dick Hertz)
Madeline (1998) [Lady Covington]: Dies (off-screen) in the hospital of an unspecified illness; we learn of her death afterwards when Frances McDormand informs Hatty Jones.