Muller was a female Galactic Empire military member, specifically a TIE fighter pilot within the Starfighter Corps. This woman was a member of Nashtah Squadron, a unit that supported army actions. Prior to the Battle of Yavin, Muller's starfighter sustained damage from an anti-aircraft missile fired by the opposing Alliance to Restore the Republic. This resulted in her needing bacta treatment, and there was a chance she would be unable to pilot again.
The character of Muller initially appeared in the short story "Last Call at the Zero Angle," authored by Jason Fry. This story was featured in Star Wars Insider 156, which was released in 2015.