Gilda wasn't always a bully. She was always antisocial and had a bit of a mean streak, but not a bully exactly. She was quite the opposite when she first moved to a city full of ponies when she was a teen, or "dinner" as she would have called them in ages past. After a while she resigned herself to exile in her temporary home, just waiting to cross the sea again. A certain annoying, gutsy, and possibly a bit insane mare changed that. We all know how their story ended; this is the day it started.
I'm aware this was probably done to death way back in the days of yore when Season 1 hadn't even finished, but I had a tiny idea to put my own little spin on it, so I figured I might as well get it out there and give it my best while I'm at it.