Hello! I am a part time english and Arts teacher, Hope this helps :)
In Mary Shelley's novel "Frankenstein," Victor Frankenstein marries Elizabeth because she has been his adopted sister and close companion since childhood, and he loves her deeply. She represents to him a pure and innocent love, and her presence serves as a source of comfort and solace to him amidst the turmoil of his life. Additionally, Frankenstein believes that by marrying Elizabeth, he will be fulfilling the wishes of his mother, who had also wished for them to be together. However, their marriage is ultimately short-lived as Elizabeth becomes a victim of the creature that Frankenstein has created, and she is killed on their wedding night.