The Frankenstein family adopted Elizabeth, and Caroline Frankenstein early planned that Elizabeth should be Victor's future wife. Frankenstein describes her character at length:
She was docile and good tempered, yet gay and playful as a summer insect. Although she was lively and animated, her feelings were strong and deep, and her disposition uncommonly affectionate. No one could better enjoy liberty, yet no one could submit with more grace than she did to constraint and caprice. Her imagination was luxuriant, yet her capability of application was great. Her person was the image of her mind; her hazel eyes, although as lively as a bird's, possessed an attractive softness. Her figure was light and airy; and, though capable of enduring great fatigue, she appeared the most fragile creature in the world. While I admired her understanding and fancy, I loved to tend on her, as I should on a favourite animal; and I never saw so much grace both of person and mind united to so little pretension. (1.1.4)Although Elizabeth does not share Frankenstein's alchemical interests (1.1.7), she is educated with him; and when Caroline Frankenstein dies of scarlet fever contracted from Elizabeth, it is Elizabeth who takes over the maternal duties of the Frankenstein family. During Frankenstein's residence in Ingolstadt, Elizabeth writes regularly, and it falls to her to describe Justine's background. Both Frankenstein and Elizabeth are active in Justine's unsuccessful defense.
On Victor's return to Geneva, Alphonse Frankenstein returns to his late wife's plan, that Victor and Elizabeth should marry. Victor agrees, but postpones the wedding until after he has completed his task. When he destroys the half-finished female creature (3.3.2), the Creature vows, "I will be with you on your wedding-night!" (3.3.4) -- a threat Frankenstein imagines is directed against himself ("I carried pistols and a dagger constantly about me," 3.5.8).
The two are married after the death of Clerval and Frankenstein's imprisonment and long illness. On their wedding night, however, Frankenstein leaves the room, and hears a scream above. He returns to find Elizabeth "lifeless and inanimate, thrown across the bed, her head hanging down, and her pale and distorted features half covered by her hair" (3.6.2).