Little Cress is pretty much just a computerized thing. When Cress was little, she recorded her voice due to her boredom and I guess she programmed it to work like that.
Little Cress is a program Cress created when she was younger, she did it wondering what it would be like to have a sister and having another person there with her.
Cress had learned, years ago, that the word satellite came from a Latin word meaning a companion, or a minion, or a sycophant. All three interpretations had struck her as ironic, given her solitude, until she’d programmed Little Cress. Then she understood. Her satellite kept her company. Her satellite did her bidding. Her satellite never questioned her or disagreed or had any pesky thoughts of her own.