Elizabeth Lavenza Frankenstein
Elizabeth Lavenza Frankenstein was the cousin of Victor Frankenstein. When she was very young, her parents died, and she was adopted by Victor's parents. When Caroline Frankenstein died, she made Victor and Elizabeth promise they'd be married one day, and both fully intended to keep this promise. When Victor refused to create a mate for his creation, the Monster, the Monster threatened to exact vengeance upon his maker on Victor's wedding night. Victor thought that the Monster meant to murder him.
He and Elizabeth married shortly thereafter. Victor armed himself to defend himself against an attack, and left his new bride in their honeymoon suite while he patrolled the house, fearing that if he remained near to Elizabeth he'd endanger her when the Monster came to kill him. He realized, too late, that what the Monster actually meant was that he'd kill Elizabeth. Hearing a scream, Victor rushed back to the bedroom, to find his wife murdered.