I don't think we have enough information on her past and how FB manipulated her to know for sure if she's a victim or not. I'm willing to believe she's a victim, even if she was willing to kill someone, but I still think it was neccessary for Okabe to do what he did, especially forcing her to confront the fact that FB had abandoned her and that she would've committed suicide. He's essentially saved Moeka's life (assuming she doesn't commit suicide that is)
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