What causes sadism and extreme violence in a woman?

This is one of the several, truly detestable and evil woman ever. Irma Grese would torture and kill prisoners for pleasure:
What would be the cause of that level of violence and sadism in a woman? A psychopathic woman that uses prolonged torture and kills for fun is rare.
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She was even more cruel than the other male prison guards.
What causes sadism and extreme violence in a woman?
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