-well that isn't enough... I do know of that line, but still her actions aren't as desperate as what the narration claims to be. Her actions, especially tone of voice, gotta match up with her desperation. I mean, she seems to be capable of thinking somewhat logically even during the moment she's about to suicide x_x;
-even if the hatred is to be explained later, you can't let it fly loose like that... x_x; Gotta drop off a hints here and there saying that there's some grudge between the two before this event.
-if you want Dennis to be self centered, there are TONS of opportunities for you to do that in your story. Also, his friendliness and his sense of responsibility as a big brother for Amy are somewhat acting against this personality of his... he seemed quite selfless and "perfect" at the moment of looking for Amy (especially when he waits for Nina to catch up and etc... it maybe better if you say that he just runs ahead of her despite of her calling for him to wait up and etc etc etc)
Well... have to go read Blue's story, then I'll come back to edit ToLaF, and then finally go see the new chapter of CoD o.o;