Malignant narcissists lie a lot. That's because their whole life is essentially a lie, and they have little regard for the truth. Many morally disordered people, however, also like to lie for no particular reason, other than the fact they can pull one over on you. I guess this makes them feel superior, and much smarter than mere mortals who prefer to tell the truth.
Some of this might also be an attempt at "gas-lighting," which is a game these deceivers play. This involves lying about various events in an attempt to make the target doubt her own perceptions, and even her own sanity. It's a favorite tactic used by malignant personalities. The name "gas-lighting" is taken from a vintage film in which a mentally twisted husband tries to drive his wife insane by moving things in their house, while insisting nothing had changed.
While we're being conned by one of these charlatans, we don't realize the number of lies we're being told. That's because we tend to take people at face value. If they say something happened, we believe it did. If they say someone said something, we trust this account. (Since my encounter with a malignant narcissist, I discount just about everything that's attributed to someone else, no matter whom says it, unless I hear it with my own ears. Actually, it's not a good practice to put words into other people's mouths, because the possibility for distortion always exists.)
Once you realize that you've been dealing with a very deceitful individual, you do begin to question everything she's said. If you've ever had the misfortune to listen to a narcissist attempt to ruin someone else's good name, this information is the first you should disregard.