Who is Jane from Xenocide and what is their importance?

Jane is truly an old friend to Ender. One of a kind, Jane exists within the computer and ansible (long distance communication) networks throughout the Hundred Worlds. Having first contacted Ender over three thousand years ago during the time he was engaged in fighting the buggers, neither he nor she knows how or why she exists. She simply is. In some senses she is like a computer program, having actual lines of code, but she also has consciousness in a way her code cannot explain. She is capable of feelings and desires but she is also able to act quite selflessly, like when she stops the Lusitania Fleet, risking of her own destruction. While she can exist or communicate with any human she chooses, something keeps drawing her back to Ender. In fact, she resembles him a great deal with respect to both her personality but also her vast capacity for empathy. She has a very special bond with another human too, Ender's stepson Miro (see below) and communicates with him through a similar earpiece.