Unless she took out the other princess, and Twilight is the last one.
Remember the red horn from King Somber survived, so if they used the last villain to somehow bring back the first one, it could still be the relative present.
Also, the clip seemed to shoe the main six in comic book super hero universe. The movie already introduce the idea of other universe, so it could be a alternate Luna.
In other words. It could be anything. Including a game by Discord.