I’LL LIVE INSIDE YOU FOREVER!  
WITH SATAN HIMSELF BY MY SIDE!  
AND I KNOW THAT NOW AND FOREVER,  
THEY’LL NEVER BE ABLE TO SEPARATE FLUTTER FROM SHY!!!

Fluttershed is only a fan personality.

now its really like the movie split

Alternate canon personalities: Discorded & Opposite Fluttershy.
 
And for fun: Fluttertree, Flutterbee, Mare Do Well, Impossibly Rich, Saddle Rager, Private Pansy, Admiral Fairy Flight, Rainbow Dash, Celestia.

Cute insane yellow horse