Context: Foster child learns to manipulate people to make them love her. She meets a kind mother for once, and she doesn't need to revert to her 'psychopathic' (for lack of a better word) side. I am thinking 'alter ego'.
Learn English – How to describe the ‘darker side’ of someone? Context given here
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Best Answer
You may use pathological:
or also refer to dark side of her personality.
(www.psychologytoday.com)