She, herself, is ancient compared to just about anyone in Bikini Bottom, including her daughter. She is shriveled up to the point where she appears to be merely a head and a spine and thus must get around by a wheelchair. She's extremely hard at hearing and has no physical eyeballs left. She is also somewhat bad-tempered and impatient, often irritating her daughter Mary.
Role in episode
When SpongeBob and Patrick come to Mary's doorstep, her mother comes forth to see what they are selling. Mary is forced to scream at the top of her lungs that they are selling chocolate bars, to which her mother reminisces on when chocolate was invented and how much she hated it. Patrick then tells her that the chocolate will make her live forever if she rubs it on her skin. Excited at this offer, she buys a bar from the boys, much to her daughter's dismay, and demands that Mary starts rubbing her with the chocolate.
Later in the episode, Mary and her mother double-date Patrick and SpongeBob at Fancy! after they become successful and rich from selling their chocolate to Tom.