Zeena's character is revealed through Ethan's memory and the action of the main story, and through hints from characters in the frame story. Wharton describes Zeena's physical appearance as gaunt, wrinkled, and sallow-faced. She has false teeth and her hair is kept in place with crimping pins. She is asthmatic and "sickly." She speaks in a plaintive, whiny drawl.
Zeena is seven years older than Ethan. She married Ethan, at the age of 28 (seven years earlier), after the death of his mother. Ethan wanted to move away from Starkfield, but Zeena did not want to live in a city where she would have no identity. Her hypochondria and her few legitimate illnesses serve as excuses for her to indulge in patent remedies and expensive visits to doctors at a time when Ethan is struggling to pay off the heavy mortgage on the farm and still maintain financial solvency. Because so much money was being spent by Zeena, there was no way Ethan could get ahead and realistically consider moving. Over the years Zeena becomes adept at using her illnesses to control everyone and everything in her environment. Her illness is the reason why Mattie must go and a hired housekeeper must come to take her place.
Zeena's rule over Ethan is powerful. She is seen as a "mysterious alien presence" and an "evil energy." Zeena is silent, secretive, and observant. When she does speak, it is to voice either a want or a criticism; consequently, before the arrival of Mattie, silence has prevailed in the Frome household. There never was and never would be any real communication between Ethan and Zeena. Zeena is intuitive; she notices everything and does not easily forget things. Ethan fears that she knows his innermost thoughts. The extent of Zeena's authority is such that Ethan and Mattie are both uneasy when reminded of her; Mattie can not even sit comfortably in Zeena's rocking chair while Zeena is in Bettsbridge. Ethan's last impression before the sled hits the elm tree is that he sees a horribly disfigured specter of Zeena's face.
Despite her undesirable qualities, Zeena responds to the tragedy with stoic endurance as she takes the responsibility for the care of Ethan and Mattie. Her thoughts about the smash-up are not revealed. Zeena continues to find fault and complain; however she is finally drawn out of her hypochondriac self-indulgence by the need to care for others.