It's not like she didn't have a motive to kill her stepfather already.
More over she was planning on doing it so how will this even make a difference.
She could make the case that killing him was in self defence as he had been rapping her for years.
The last girl will be the hardest to kill, but if she doesn't care about living she should be able to do it however she wants.
Thanks for the translation
Asher Does A Scan