I would say that, given the wing size, horn length, tail length, and taking into account that while her mane is short it is somewhat frazzled and a couple of strands along with her tail are much longer than the rest, I would say this is in the future and Twilight just had a little mental breakdown.



She cut her mane short very quickly to the way it used to be, ran off into the woods, collapsed, and is only now coming back around and noticed the rock which must have been here long before she was, and by finding something as old as herself she finds some solace.



Not sure what the extended wings might represent.