Nightmare Moon behind the statue, whispering to herself: "And all is my fault… so sorry sister…"
After rewatching the series (for my timeline, a particular scene jumped out at me. It was during the episode from season two to episode 4 "Nightmare night", and especially this scene exactly where Luna tells Twilight that she was exiled to the Moon for a thousand years. In my universe, Moony merged with Luna,forced by forbidden magic, and are both going to the Moon.
When Luna regains her senses, Moony has always been left in the shadows with her remorse and shame for the action she has done to her sisters.
And when Luna says "We", in the series just describes the royal us, for my universe the us had a whole other meaning.
We are Luna and Moony. Suddenly, Luna says half-word that she regrets her sister and her action she made (because no one, not even in the writings in that Equestria shows Nightmare Moon as a sister, I will explain to you when my timeline project is finished) then that Twilight thinks she's using the us royale.
Behind, Moony, living only in Everfree Forest (because she knows him like the back of his hand), was there when Luna cried in front of her statue. Afraid to approach her, afraid of the consequences, and afraid of being missed by her own twin sister.
Have a nice day!
And don't forget to watch me for more!