The files include the following cosplay accesories: a crown, two horns, and Bowsette's jewelry which are earings and a brooch.You'll find a version of the crown that is one whole piece ready to print, and another version that is split in several parts. To print the earing I just upsized the balls that are part of the crown, as shown in the photo of the prints I made they look ok.

Bowsette, as the internet has named her, is a character merge inspired by the idea of Bowser using the Super Crown from New Super Mario Bros. U Deluxe to transform into a Peach version. She appears to have originated from the work of artist aykk92, who sketched an amusing comic strip imagining a spurned Mario and Bowser finding love using the Super Crown.