From Halopedia, the Halo wiki
Mission aboard Mona Lisa
She was part of Sergeant Zhao Heng Lopez's squad assigned to investigate the prisoner transport Mona Lisa in the debris field of Alpha Halo over Threshold. Unbeknownst to the Marines, the mission had been commissioned by the Office of Naval Intelligence, whose operative John Smith had been secretly using the ship as a laboratory to research the Flood.
After the Marines boarded the Mona Lisa, they were immediately engaged by several unarmored Covenant Sangheili in the ship's cargo bay. During the skirmish, Rabbit and Mahmoud killed one of the Sangheili. According to Mahmoud, Rabbit would then say something indistinct before another hostile appeared and Rabbit went missing. Rabbit was actually attacked by a Pod infector, becoming the first victim of the Flood in Lopez's squad. The other Marines would soon after discover her body in a shower block, with a Sangheili stomping on her chest, mangling her torso beyond all recognition in order to destroy the Flood infection. After the Marines had killed the Sangheili, Lopez would dig up Rabbit's dog tags from her crushed innards, also finding a mysterious, decidedly non-human appendage from the remains.
List of appearances