User blog comment:Miskos3/Fairy Tail Chapters 532 & 533, Review/@comment-7070784-20170422053208/@comment-5303512-20170425160816

Alright, you want proof, here it is

http://m.mangahere.co/manga/fairy_tail/v02/c009/11.html

Read all the way to page 15.

Lucy explicitly explained that it was the book that contained all the letters to Coby, even while under the spell. That means she deciphered the real message behind the book while as Daybreak and knew what it really was. She knows how books and writing works.