Eleanor is self-assured, cute, sweet, confident, obedient, and extremely maternal. She is a gifted athlete, despite her larger physique. Eleanor is quite strong-willed and is far more likely than the timid Jeanette to stand up to her sister Brittany when she feels that she is wrong.
Eleanor gets along great with Theodore of The Chipmunks. They are very open about their relationship and have many similarities. For example, they both love food and are interested in cooking.
Eleanor's age in regards to her sisters is never stated in the films. Despite not having a stated last name either, it is presumed to be Seville because of The Chipettes being taken in by Dave at the end of the second film. However, this naming would be controversial, as it would make her Theodore's adoptive sister in addition to his love interest.
Eleanor has a much softer and childish personality; she acts almost exactly like Theodore and seems extremely naive.
In the second film, Eleanor arrived, along with Brittany and Jeanette, in front of the residence of former big-shot manager Ian Hawke. He agreed to manage them, as well as adopting them. Eleanor expressed the most interest in meeting the Chipmunks, especially Theodore, but was discouraged to do so by Ian with his lies. After enrolling in West Eastman, she finally got to meet him face-to-face, falling in love with Theodore. She continued to show eagerness in hanging out and getting to know him and the other Chipmunks, but her hopes were constantly being squashed by her manager. Ian was very cruel to her, making a rude comment about her weight and making her feel bad about her height. She and Jeanette were pushed further away from Brittany because Ian showed favoritism toward her. Though she was hurt by this, she held nothing against Brittany and decided to keep quiet in order to reach their dreams of becoming big.
Eleanor's age in regards to her sisters hasn't been stated in the series so far though she retains the last name Miller as stated in Jeanette's Secret Garden.
Eleanor in the ALVINNN!!! and The Chipmunks series is much like the Eleanor of the 80s series, though it’s taken to the next level. She lacks the insecurity about her weight as was portrayed in the CGI films and once again shows off her cooking abilities (Jeanette Enchanted), maternal instincts in treating the injured (What A Gem), athletic fitness (Family Spirit), and disdain for Brittany when she acts to dismiss Jeanette (My Sister The Weirdo). Despite being tomboyish she has shown several traits more commonly found in typical girls: she cries for sappy moments (Summer Camp), wears a skirt, has taken ballet lessons along with her sisters (Ballet Boys) and can be scared easily, even when she knows she was part of a scheme of scaring someone (Monster Madness). She is also seen to be a little more hotheaded compared to her previous incarnations (Sherlock Chipmunk).
In the Alvin and the Chipmunks series, she has blonde hair in pigtails and brown eyes. Her signature color is spring green. She usually wears a light green/blue dress with a white long-sleeved shirt underneath, with a striped tie, and knee-high socks with black shoes.
In the CGI films, Eleanor has green eyes. She has blonde/yellow hair in pigtails. In Alvin and the Chipmunks: The Squeakquel, Eleanor wears a dark green sweater over a light green dress and a silver sparkle dress. In Alvin and the Chipmunks: Chipwrecked, she wears a green and white striped shirt with a green skirt with black dots, as well as a green-sparkle dress and green-flowered garments. In Alvin and the Chipmunks: The Road Chip, she wears a green and white striped shirt with a green skirt with dark green and light green dots.
In ALVINNN!!! and The Chipmunks, her hair is blonde/yellow in pigtails, and she has green eyes. Her attire frequently consists of a light green and dark green striped shirt, with a spring green skirt, and light green sneekers with white laces.
Eleanor always stands up to Brittany when she tries to push Jeanette around, and always defends her when anyone says something negative. For example, refusing to help Brittany join a group that called Jeanette a 'nerd'.
Eleanor always stands up to Brittany when she tries to push Jeanette around, and is generally the only person that tries to stand up to Brittany (besides Alvin). The two of them do share a very nice sisterly relationship.
Eleanor and Theodore are the most open about their relationship. They spend lots of time together and enjoy the others company. In Meet the Wolfman, Theodore gives Eleanor a necklace. They are shown to be married as adults in Big Dreams.