She’s ready to shoot ‘em all up. If that’s okay with them.

Fluttershy: (to Garrus Vakarian) “I’ve got a shotgun.”

“Don’t move, or I’ll shoot!
 
“…O-of course, unless you don’t want me to….”

Stock packed tight into the shoulder, lean forwards into the weapon, and keep the trigger finger away from the trigger until it is time to squeeze it. It’ll make a big noise, and it will kick, but it won’t cause any harm to you unless you mishandle it. It will especially not cause any harm to anyone else unless you allow it to.
 
Gun safety is critical. It is as important as learning to safely operate any tool in existence, from lawnmowers to can-openers. If one doesn’t learn to operate a tool correctly, someone will get hurt.

Someone needs to start dressing up the Equestria Girl characters as the 3rd Street Saints.
 
And while we’re at it, let’s have a Equestria girls version of Johnny Gat.

Looks like she’s going to put down Angel.

You’re holding that shotgun wrong. You’re going to dislocate your shoulder or elbow, ’Shy.