The police won't believe her, and knife boy will eventually have all the killings pinned on him.
And it will be on purpose, because by that time he will understand that accepting the penalty for killing her father is important to her. He will want to deprive her of her amends.
Code:
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Edit: I don't think it'll be pinned on her, nor would she be suspected (the guy ran away with the knife and more importantly, witnesses), but she's gonna take a helluva hit mentally.