Got inspired to try and draw some sort of formal wear for Mei. She comes from an old and traditional town, so I'd image their formal wear is equally old and traditional rather than something more modern - hence, Mei dressing up in a Hanfu, and taking an inordinate amount of time to admire herself in the reflection of a pond.
It's an old Chinese type of dress similar to the Japanese kimono and Korean hanbok. There should, probably, be all sorts of elegant patterns over the hanfu, but I had enough trouble just trying to design the thing on a pony body, lulz. Any sort of outfit that has a high-waisted style is kind of moot on a pony, seeing as their "waist" is underbelly. Still, it was a fun design, and one that'll probably serve as Mei's formal wear should the need arise.