Amanda is a member of the Sandinstas in MGS: Peace Walker. Her father, the leader of her group, recently died in battle and Amanda has taken over the reigns when Snake (Big Boss) meets her in Bananal Fruta de Oro. Shortly after the metting she breaks her leg in the battle against Chrysalis and it's kidnappers and is left in a critical condition after Snake shoots down the second kidnapper that captures her. Agrees to go with Kazuhira Miller back to Mother Base, where she stays in the sick bay. Amanda provides valuable information on the missions you undertake in her home country. Her first request is to find her younger brother, Chico, who has been abducted by the enemy, La Cia (The C.I.A.) along with her "compas" for questioning. After Mother Base became the target of Peace Walker's nuclear strike, her and Chico had to leave Motherbase and fight the KGB in Nicaragua.
Amanda is not present during Metal Gear Solid V: Ground Zeroes, but is mentioned as still allied to Snake and Miller in the game and that she is off-site. A potential appearance in Metal Gear Solid V: The Phantom Pain is unknown.
Gameplay-wise, her injuries will not heal past 20% until after Chapter 4 is completed unlike normal soldiers left there. Her stats (and contributions to Mother Base) suffer temporarily the longer she is out of sick bay, so be sure to put her back in every few missions. Her unique skill increases the morale of the Combat Unit when assigned there. By S-ranking Extra Ops 67: Date with Paz, the player can unlock Amanda's uniform, usable only by female soldiers. In one of the cutscenes, if the player refuses to shoot the kidnapper that captured her she will kill herself, resulting in a Mission Failure.