Scene from "Survivor Shy", a story that follows Fluttershy living in a world completely and suddenly devoid of other ponies.
With nopony to turn to, Fluttershy is forced to learn to fend for herself, and find a way, if possible, to bring back ponykind and save Equestria.
I've recently began a massive overhaul and partial rewrite of the story on FimFiction, the story should be much easier to read and make sense of now :)