Well, she came out as a Pony...so at least this is not an universe with some other species taking the place of them.
Welp, it’s suddenly exploding
Hm, could we be seeing one of the universes from when Princess Twilight and Starlight were messing with time? To see that those individual timelines just diverged off to their own mirror universes?
OH GOD, SOMEONE SUMMONED CTHULHU!
Equestria Prime? I think not.