Eleanor Lamb is major character from BioShock 2.
She is the daughter of BioShock 2's primary antagonist, Sofia Lamb. She is also a Little Sister, her Big Daddy being Delta, BioShock 2's primary protagonist.
Throughout the course of the game, she leaves him gifts and messages written on the walls of the city, and also makes frequent contact through radio messages, which allows Delta (the player-character) to track her down and rescue her from Sofia.
Delta's influence over here is immense and, depending upon his actions throughout the game (saving or harvesting Little Sisters, and killing or forgiving certain NPCs) she will either turn out to be a gentle, caring girl, or a dark, selfish one, which in turn goes on to shape her as a person for the rest of her life.