Petra is one of the few female students at the
Battle School. As something of an outcast herself, she acts as an older sister towards
Ender Wiggin and teaches him how to shoot. In fact she may, in the beginning, have identified with
Bean because in many ways he was so similar to Ender (small size, amazing genius). In
Shadow of the Hegemon, it's mentioned that one of her teachers found her so aggressive that he actually had her genome scanned to make sure she wasn't a boy.
Petra becomes a member of Ender's "jeesh," or informal team and as such she rejoins him in
Command School, where she serves as one of his most capable lieutenants during the campaigns against the
Buggers. He relies on her so heavily, in fact, that he pushes her too hard and she finally breaks during combat, dozing off from exhaustion and causing a number of casualties. Although she recovers, she loses her aggressive edge and she never quite trusts herself again, believing herself to be weak and unreliable, a judgment that later events prove wrong. It is shown at the end of the book that Petra might have some attraction to Dink Meeker, and vice versa.
While she is Armenian in the novels, Frank Miller re-wrote the character to make her Chinese. He felt this added to the international appeal of the work, and made casting for the part much better for Robert Zemeckis as well

.