There have always been two of them. Two polarities of one whole. Two opposites in one body. Good and evil. Light and darkness. Creation and destruction.
Whether she wanted it or not, this addiction will be in her forever.
Good is learned through evil, night is replaced by day, cold is followed by warmth, the sun is replaced by the moon, sinfulness calls to holiness, strength is created from weakness, intimacy is built from loneliness...
Whichever side wins, she will lose. There is only one way out. Let the two of them live and stop this fight.