Despite a malignant narcissist's desperate attempts to make you believe that, somehow, it was something you did that set the relationship on a collision course, this is not the case. Disordered people are unable to maintain healthy friendships. It's this reason, and this reason alone, that the two of you are no longer "friends."
Of course, you might have rushed the inevitable a bit. Challenging a narcissist on her bad behavior, or merely questioning her actions, might be enough to make her cut you out of her life forever. When this happens, the narc goes into full discard mode, and will tarnish your good name all over creation. She'll also attempt to draw as many people as possible into the drama. Normal people do not behave this way.
Narcissists discard "friends" and acquaintances over very trivial matters or for no particular reason, other than they tire of your company. This typically happens after they've recruited you for a certain purpose, and, now they no longer need your help. One thing to remember about malignant personalities is that they view others almost as objects, to be used and then tossed away when they're finished. They are also adventure seekers, so they get bored with people very easily.
Realizing that this "friendship" was going to end, no matter what you did, is one of the first steps toward bouncing back from an encounter with a narcissist. This is the type of destructive force you don't need in your life. Some researchers believe malignant narcissism and sociopathy are indistinguishable. Goodbye and good riddance.