She said she didn't want to see her mother, but then she agreed that they'd go to DC and find her. That's why they are walking to DC. She shouldn't have agreed if she wasn't really willing to do it. Sammy is not really great for continuing to insist on it after Hero explained she didn't want to, but their lives are in danger so I can get that.
The death was an accident, but she still threw a sharp metal object at a person's head. I didn't say she murdered him, just that she killed him. I agree most people are capable of killing someone under certain circumstances, but not everyone would p