Who is Petra (Arkanian) Delphiki from Shadow of the Giant and what is their importance?

An Armenian, Petra Delphiki is a former member of Ender's Jeesh. In fact, she was one of the most ambitious and valued members of the Jeesh, but when Shadow of the Giant opens, Petra is the pregnant wife of Julian Delphiki (Bean), who she met in Battle School. He, too, was a member of Ender's Jeesh with the distinction of being the smartest and least ambitious student ever to attend the school. Petra has set aside her own ambitions and is pregnant with Bean's child through in vitro fertilization. The remainder of their fertilized eggs have been stolen, and Bean and Petra use every avenue and resource to find them. Bean's time is short, because his genetic modifications are likely to kill him by the time he is 20-years-old.