The Girl Who Pretended To Be A Boy, from The Violet Fairy Book compiled by Andrew Lang, on Project Gutenberg.

Just.  You guys.  IT’S A CLASSIC FAIRY TALE ABOUT A PRINCESS WHO GETS TURNED INTO A BOY AND IS SUPER FREAKING HAPPY ABOUT IT AND THEN GETS TO MARRY THE PRINCESS SHE RESCUED. 

Thank you, Seanan McGuire, for mentioning that a story like this existed.  And thank you, whoever that person who sent her an ask saying the story was in one of the Fairy Books, for sending that ask.

I AM SO HAPPY OMG.