Charming in public: exuding warmth and charm, she smiles and tells jokes, praises and flatters you, outwardly supports you with a show of approval and reassurance, makes you feel valuable and appears to be your friend, appears to be supportive and attentive to your needs. She always appears to be helpful.
Rumor-monger in private: criticizing you behind your back, she may suggest that you have personal or emotional problems, carefully building a case against you via calculated misinformation passed on to others behind the scenes. She manipulates others into criticizing you and then rewards them for their participation in her plot to undermine your image in every way.
Two-faced: She pretends to support you while planning to destroy you; then when you challenge her, she suddenly transforms from supportive to bullying. Her soft-spoken manner hides her destructive intentions, her flattering words hide her desire to control you, and her seemingly warm personality hides her take-no-prisoners attitude.