Yepp, the BGStory for her turned out like expected. Sure, she is a child and everything and you shouldn't judge children too harshly, but she is still trash. When it came down to it, she resorted to violence. And betrayed her childhood friend. No matter how hurt and betrayed she felt herself, that went lengths too far. You can forgive someone something like that, if that someone is an underdeveloped character, who is overwhelmed by the circumstances and was in an especially bad situation. Forgive it once, if it happened once. But she did it continuously.