Internet issues. At the time orson Scott card wrote this book, the internet didn't exist. He does point out some potential flaws of such an internet system if it did exist. What might those problems be that Peter has already figured out?
Valentine is commissioned by Graff to try to help Ender, though he is unsure what she can do. He tells her about the fantasy game and Peter's picture, but Valentine does not understand why Peter's picture would show up--she thinks Ender and Peter are nothing alike, since Peter is evil while Ender is good and would never hurt anyone. Graff suggests that Peter and Ender are more alike than she realizes. She says that she often reassured Ender that he was not like Peter, so Graff suggests that she write to Ender to reassure him once again. She does, and later she regrets selling out her brother, despite receiving a high civilian award for her service.
Ender receives the letter, which includes signals proving that it is really Valentine's writing. But he grows upset when he realizes that Valentine has become "one of them now," agreeing to the adults' plan. He perceives that the adults now know all about his feelings about being like Peter and about the mirror in the game.
It is interesting that Ender and Valentine share a similar reaction to the fact that she wrote the letter to him for the International Fleet. He feels like she betrayed him, that she became one of them, just another tool for Graff, and she feels the same way, saying that they "paid" her for selling out her brother. Despite their disgust, Ender does change after reading her letter, understanding that Valentine did intend to help him. In the game, he chooses to kiss the snake instead of killing it, choosing love over hate.
