Luna in charge?

My Ponies,

I remember the time when I was free, ruler of my land and keeper of peace. Now I was salved by Luna, my sister who I always loved. It was not the nightmare that was inside her long before, it was her true form Moonlight Swept. I had not known she could be what she had become, but it had happened. I am going away forever very slow and in pain. I wish for the ponies I love to be safe. My dear ponies be safe for that is all you have. Love is the key and flee

                                                                                  Your Princess,

                                                                                                            Celestia

The Princess died and Twilight was never to be seen. The letter got out, but to whom is uncertain.

My Ponies,

I am now my true form, MOONLIGHT SWEPT and I am here to give you ponies some proper teaching. Hope that some ponies can fly at night.

                                                                   Your NEW Princess,

                                                                                              Moonlight Swept

Twilight read the note and felt anger.