The book was "The Woman in White" by Wilkie Collins. The book does not actually feature a princess, but a woman in a long white gown on the cover, who the little girl thought was a princess.
Of course, the book is just a bit above her reading level. She just liked carrying it around, her mom, who asked that she and her daughter not be named, told BuzzFeed News.
"I like old dead British writers, so I have a lot of them, and she just loves the cover. So naturally, we carried it around with us for a week on end," she said. "It was her princess book, and she would sit and pretend to read it."