I do love those Princess Ponies
You are right, in that the hat was intended for Princess Aquamarine (UK) or Princess Tiffany (US) depending on the distribution.
I do know MLPSunsparkle has found wild princess variants including a variant Amethyst and SunPearl, so that also leads me to think it is variant rather than a ribbon swap. The texture of the ribbon looks right to be variant as well
Here is a link to Shelti's ultimate Princess guide
http://www.princessvariants.com/PPCATALOG/PPCatMain.htmlLove pkw xxx