People with malignant narcissism are very mercurial. They can become enraged over nothing. Part of the reason for this is that they have very fragile egos, and, if they feel as if they are slighted, they turn into monsters.
You may not have done anything to set them off. This happens because they process information differently than the rest of us. Even a perceived slight is enough to set them on a rampage. So don't tie yourself in knots, worrying that you should have done something to avoid this reaction. Once you get involved with a narcopath, it's always going to end badly, no matter what you do. That's because people who suffer from this terrible personality disorder have extreme trouble maintaining healthy relationships.
Morally disordered individuals are initially drawn to people with high levels of empathy (something they lack). They know these "empaths" will serve a purpose. They may want your help in some way. Perhaps you are in a position to advance their career. Or, maybe you know a lot of people, whom they find interesting. In that case, they will use you for the introductions. Then, then will seize whatever it is they wanted.
There is nothing you can do to stop narcissistic rage, which is almost always irrational. During the discard phase, when the mask comes you, is when you'll see a narc's ugly side full force. She has no need to maintain a facade in your presence, since she no longer has any use for you.
By the time this happens, she has already moved onto the next victim. During her interactions with the new target, her mask is tightly secure, and she showers this new "friend" with all the attention she once reserved for you. The pattern then repeats itself.
Consider yourself fortunate this person will soon be out of your life. Distance yourself from this malignant individual as much as possible. Enjoy the peace that will once again flow through your life.
Pixabay image top by Nemo