Morally disordered people are never satisfied with what they have. They want more and they're always on the lookout for new acquisitions. The fact that you own something makes it all the more attractive to them, especially if it's something you hold dear. Your possession might include having a slightly nicer house than the narcissist. If that's the case, she'll be seething with envy. Or, you might be very competent at your job, and this is obvious to everyone else in the department. To "remedy" this situation, she will try to undermine you and even drive you out of your position.
Female bullies operate on the principle of social aggression. If you're their target, they spare no effort to destroy the relationships you have with other people. This is exceedingly cruel, because it leaves you without a support system. All but the most loyal friends will fall for her ploy. In fact, when a malignant narcissist decides to attack, you find out who your true friends are, because she'll try to "buy" each one of them off with favors and inclusion into the social network that she controls. Only the most true blue individuals will see through her act and not going along with her attempt to ostracize you.
If someone adopts a position of neutrality, they are not true blue. Instead, they are an enabler.
The person the narcissist will try the hardest to recruit will be your best friend, if you all belong to the same social circle. That's because narcissists are so covetous that they want this relationship all for themselves. Everything you have they want, and they will stop at nothing to take it away from you.