It’s an unused panel from the “Newcomer” comic.
 
At first I planned to finish this “story” earlier, and it would have ended with Fluttershy at the window making a comment on what she just saw.
 
But instead I decided for a longer and more emotional approach for the “ending” of this comic, so this panel lost it’s use.
 
I also have to add, Fluttershy’s expression doesn’t look exactly how I planned it, and I probably should have added some blushing, but it’s an unused panel, so I guess it doesn’t matter that much.