Selma Livens belonged to the elite Brown Southern Cross team in the Principality of Zeon's military forces. She served under Cucuruz Doan's command until his unexpected desertion, after which Egba Atler led the unit. Despite Egba's open hostility toward the deserter, Selma maintained a positive regard for Doan. The exact nature of her feelings toward him remained unclear, interpreted as either professional respect or potential unrequited affection.

As the pilot of Unit 2, she operated a brown-camouflaged MS-06GD Zaku II High Mobility Type (Ground Use), equipped with a Type B2 MS bazooka and heat knife. The Southern Cross gained notoriety as feared Zeon remnants after combat victories in North Africa, including a decisive clash in Casablanca that destroyed multiple Federation GM mobile suits.

Her final mission occurred when M'Quve dispatched the unit to Alegranza Island to investigate signal jamming at a hidden nuclear missile base. There, they confronted Doan, who actively opposed their attempts to activate the missile launch sequence. Despite any personal reservations, Selma engaged in combat against her former commander. She perished when Doan's heat hawk destroyed her Zaku. In her dying moments, she tearfully demanded to know why Doan had abandoned the team.