Little is known about Emma Sheen prior to the events of Zeta Gundam, though we do know that in her youth, she had a chance meeting with Amuro Ray on earth.

At the start of Zeta Gundam, Emma is a Lieutenant Junior Grade in the Titans. She defects after Kamille Bidan's mother dies in a brutal display of Titan tactics. After arriving at the Argama with all three MK-II prototypes as a display of her loyalty, she witnesses the deserted Colony 30 at Side 1, where the Titans used lethal gas to stop a demonstration being held there, with the loss of all 10 million colonists.

Established as a loyal ally, Emma becomes a regular pilot, using the RMS-099 Rick Dias and later, the hand-me down RX-178 Gundam Mk II, which is upgraded via G-Defenser attachment to 'Super Gundam' towards the end of the series. She is often contrasted with Reccoa Londe, who defects from the AEUG to the Titans in the later half of the series and turns out to be Emma's ultimate opponent.