Ellen Ripley was an advanced synthetic duplicate of the original Ellen Ripley who died on Fiorina "Fury" 161 in 2179. She helped Corporal Wilks and Billie battle the Xenomorph menace. She was active during the Xenomorph infestation of Earth in the 2190s.
Behind the Scenes
Originally, the synthetic Ripley character was in fact the real Ellen Ripley from the film series; the early comics in which the character appeared were a direct continuation of Aliens's story, featuring Corporal Hicks, Newt and Ripley continuing the fight against the Xenomorphs. However, following the release of Alien3 in 1992, in which Ripley is killed on Fiorina 161, the character from the comics was changed to be a synthetic double so that the stories in which she features were still compatible with the film series. This change appeared in the novel Aliens: The Female War, an adaptation of the first comic series Aliens: Female War. However, while the other early comic books were subsequently edited to reflect the new character identities, Ripley in Female War was not (likely because changing her to a synthetic would require a significant expansion/alteration of the comic way beyond simply rewriting names). As such, even the current edited versions of the comic book offer no explanation as to how Ellen Ripley could still be alive post-Alien3. Only the novel includes the extra material regarding the discovery that she is an android duplicate, and her subsequent struggles with this revelation.