Martel

Martel (マーテル, Māteru), known as Marta in the anime, is one of the many chimera to work with Greed. She was a soldier of the State Military who was turned into a chimera; in the anime this was done to keep her quiet about her secret missions, while in the manga it was because she was severely injured by a land mine. Martel was crossed with a snake, and thus can stretch and contort her body to great effect. She uses this ability during her introduction to infiltrate Alphonse Elric's hollow armor body and control it from the inside. She remains in Al's body for much of her role in the series, the most prominent reason being that she is safe while in there. In the manga, Martel is killed during King Bradley's attempt to capture Greed; shes tries to use Al's body to kill him for slaughtering her fellow chimera, only for Bradley to cut through Al's armor to get her. In the anime Martel survives this raid and accompanies Al in his various endeavors. She is ultimately killed by Bradley in much the same way as in the manga, though not before informing Al that Bradley is a homunculus.

Source: Wikipedia