|East Side, West Side (1949) [Isabel Lorrison]: Strangled (off-screen) in her apartment by Beverly Michaels; her body is shown lying on the floor afterwards when Van Heflin investigates the crime scene.
Pandora and the Flying Dutchman (1951) [Pandora Reynolds]: Willingly sacrifices her life in order to let James Mason's ghost rest in peace. (I have not seen this movie myself, but got the information from the book The Films of James Mason.)
The Snows of Kilimanjaro (1952) [Cynthia Green]: Mortally injured by an exploding shell; she dies (off-screen) after being taken away on a stretcher. We learn of her death when Gregory Peck is informed. (Thanks to Tony)
The Barefoot Contessa (1954) [Maria Vargas]: Shot to death (off-screen), along with her lover, by Rossano Brazzi. Her body is shown afterwards when Humphrey Bogart runs out and finds Rossano carrying her body; Rossano then carries her body into the house and sets her down on the couch, all the while telling Humphrey about his crime.
The Naked Maja (1959) [Duchess of Alba]: Dies of a terminal illness. (Thanks to Howard)
55 Days at Peking (1963) [Baroness Natalie Ivanoff]: Shot in the arm by a Chinese soldier; she dies of the resulting infection some time later with the doctor (Paul Lukas) at her bedside. (Thanks to Farzad)
Earthquake (1974) [Remy Royce-Graff]: Drowned after being trapped in a flooding chamber. (Thanks to PortsGuy)
A.D. (1985) [Agrippina]: Stabbed in the stomach by Anthony Andrews' henchmen. (Thanks to Gordon)