Unlike the majority of the areas in Tickington, this one isn’t unlocked by finding a Tockle in the world. Instead, you simply need to finish Chateau Felix in order to have access to it.
Upon visiting this area, you should see Jessica from Dragon Quest VIII, as well as her mother. It seems that Jessica is acting weird, so speak to her mother and she will ask you find something to change her daughter back to normal, giving you the quest called Mother Knows Best. There are two books that change personality, although one is the wrong choice. If you picked up the Guns ‘n’ Buns book from Briscoletti’s Mansion, give it to Rosalind for a nice laugh or two.
For the correct book, you will need to have access to the Quester’s Rest area of Tickington. When you do, search the bookshelf on the right side of the room there to find the The Girl’s Own Annual book. Give this one to Rosalind to finish the quest, who will hand over the Goddess Whip as a reward. This is a pretty strong whip, though, being stronger than most weapons for the characters that can equip whips.