Use the leverage of your own expertise or productivity to keep the NPD (narcissistic personality disorder) person's behaviors in check. Be cautious as you offer your advice, remaining vigilant about what the NPD individual wants from you. Remember that any honeymoon period of cooperation you have with this person will last only as long as you have something she wants from you. Steel yourself for the moment when she projects her difficulties onto you. Be ready to stand up for yourself calmly and firmly without the expectation that she will acknowledge your position. For emotional support, utilize an outside support person (preferably outside the work setting, or an ironclad safe person within the work setting) who can validate your efforts and encourage you to stand up for yourself.
-- Eleanor D. Payson, The Wizard of Oz and Other Narcissists, p. 148-149