I'm glad to see Hinako admit that she's a murderer. But that admission, makes her goal of finding her older sister, pointless if she wants to kill her a 2nd time. She shouldn't have killed her the first time. Zero self control. You can choose not to forgive someone, and also refrain from murdering them. Is she an animal with no self control? Killing her a 2nd time, isn't going to provide any catharsis or closure. The only motivation that makes sense for seeking out the older sister, is for Hinako to apologize for killing her. I hope the author doesn't make the older sister into some super evil character, just to assuage Hinako's guilt.
Hinako is telling herself lies. Yes, she is a murderer. But that doesn't mean she can't try to make amends and do good. Which she already is doing with saving the town, and comforting the dying boy. The lie she tells herself, and others, is that its just her job and to set a good example for her little sister. She clearly cares about other people.