Parental alienation does not end at the age of 18. Alienated children often become lifelong foot soldiers in the alienating parent’s campaign of hatred and destruction. I suspect that, if some form of personality disorder is at play with the alienating parent, that it may become manifest in the alienated child – either through genetic heritability, modeling or both.
The questions I ask in every case are, “If this person weren’t your mother or father or sister or brother or daughter or son, but were a colleague, acquaintance or friend and they treated you like this, would you have anything to do with them? Would you continue to turn the other cheek or would you cut them out of your life like a malignant tumor?”