Deviant behavior does not arise out of the blue. It is a pattern that's repeated, usually throughout a person's life. A female narcissist did not just suddenly decide to abuse someone. This is something an adult bully most likely been doing since childhood. Because it served her so "well" to mistreat others, and to engage in mind games, she "perfected" her "skills" and turned them into an art form.
A morally disordered person with the propensity to hurt someone does not stop when her target is neutralized or destroyed. She needs the rush and exhilaration that come from inflicting pain. So, after a short breather, another target will be chosen. In the workplace, this typically happens after she's managed to either drive her last rival out, or connive long and hard enough to get her fired. She'll strike again, because she won't be able to exist without the constant drama. Why management won't step in when they realize one person after another is leaving is something that mystifies me. It is very expensive to keep having to hire and to train new people.
I realize narcissists are extremely crafty and deceptive, and that they project their bad deeds onto the target. But, after a while, you'd think that someone would wise up. The only explanation that makes sense is that narcissists are so charming, and command such a presence, that those in a position of power to make things right are either afraid or totally taken up with the abuser.
But, anyway, these folks operate in a fairly predictable pattern. When you're dealing with an adult bully, you can rest assured that you aren't her first victim and you won't be her last. She'll have a long history of causing upheaval where ever she goes.
The chaos also carries over into her personal life. If she has children, unfortunately, they are suffering tremendously. At the very least, they are very neglected on an emotional level, although one of them might be chosen as the "golden child" and groomed to be a mirror image of her mother. She will then direct her attacks toward her siblings.
Psychologists believe malignant narcissism is a permanent disorder that has no cure. I agree, to a point. If someone repents of their behavior, and turns to God, he can transform them into a much different person.