|Voyage to the Bottom of the Sea: The Price of Doom (1964) [Julie Lyle]: Killed by a giant plankton creature as she backs through a hatch while holding the crew at gunpoint. (Thanks to Stephen)
Violent City (Citta violenta; The Family) (1970) [Vanessa Sheldon]: Shot in the head with a sniper rifle by Charles Bronson while riding in a glass elevator; her body is shown again afterwards when the elevator arrives at her office.
From Noon Till Three (1976) [Amanda Starbuck]: Commits suicide by shooting herself. (Thanks to Thomas)
Love and Bullets (1979) [Jackie Pruit]: Shot in the back by a hitman. (Thanks to Robert)