"Perhaps, you have something on her that you could use as leverage in this situation. Or treat her like a kid using reward and punishment system. Tell her if she does this, she won't get that :-)."
Unfortunately, the "Reward/Withold" tactics are the same strategies that the abusive narcissist uses to rope and throw their victims/supplies. The whole idea of becoming educated about narcissism, traits, damage, and strategies is to break the cycle of abuse and employ common sense.