Deatails and selected screen captures of death on the silver screen sorted by performer...
From time to time, I've noticed a couple of questions that come up in movie trivia discussions: "Has so-and-so ever gotten killed in any movies?" and "What's that movie where what'sisname kills such-and-such?" This site will attempt to answer those questions for most of the so-and-so's, what'sisnames and such-and-suches. (I've even started listing voice-over performances in animated death scenes.)
The Night Evelyn Came Out of the Grave (1971) [Gladys]: Poisoned by her boyfriend, she manages to stab his accomplice/lover (Erika Blanc) before dying.
All the Colors of the Dark (Tutti i colori del buio; Day of the Maniac; Demons of the Dead; They're Coming to Get You) (1972) [Mary Weil]: Reportedly stabbed to death (off-screen) by the cultists; there is an earlier scene in which Marina apparently commits suicide by throwing herself onto a knife that Edwige Fenech is holding, but it's suggested that this was a faked death. (Thanks to Johan)
The Mothman Prophecies (2002) [Mary Klein]: Dies of a brain tumor (discovered when she's checked for head injuries after a car accident). Although there are several scenes of her in the hospital, her actual death is off-screen; we only see Richard Gere being informed of her death afterwards.