Big Sister
Summary
A term coined in the years after the third world war on Earth, "Big Sister" refers to a supposed non-aligned, international "Super-Spy" organization blamed or credited (depending on your point of view) with starting the war in a supposed attempt to overthrow the formal governments of the world and "free" the citizens.
"Big Sister" was supposedly an opposing force to "Big Brother" the generalized term taken from the novel Nineteen Eighty-Four, by George Orwell, among anti-government-minded people before and after the war. Though the name never really caught on in the general population, it remained in use among the would-be followers of the fictional super-spy organization. Alternatively, the term "Our Friend" in various languages was also used to refer to this nominally female persona.
In reality, the moniker "Big Sister" was a term promulgated by one of the virtual personas run by the Celest computer software before, during and after the war. Although she retired most of her "virtual people", Celest kept one or two around at all times to act on her behalf when necessary. It was the virtual person "Emma Rogers" of the U.K., a closet sympathizer of The Friends who is credited with first coining the term. Naturally, none of The Friends ever actually met Emma in person, though she had a social media profile, pictures and even video content of her graduation from College on her social media pages - all of it generated by the AI, but she was never real. As with most of these virtual personas, Emma eventually disappeared, along with all her social media information and among The Friends it was generally believed that "...the government got to her".