I'm pretty sure all those costume bits are available in-game too. Nice.
Bunny Crown from the Gold Saucer, Sailor Shirt made by a Level 50+ Weaver, and the Valentione Skirt and possibly Valentione Pattens from, well, a previous event and/or the MogStation. Not sure what gloves're being used, though, but I imagine any would suffice with Pure White Dye.
You would be entirely right that this is entirely possible!
