Yeah, clearing the Feared Kjeldar Castle is not recommended before completing the 3Dazer, as the fights are much easier afterwards, the trapped chest is survivable with stronger characters, AND Christine doesn't appear until after the 3Dazer! She isn't the Christine from the House of Pleasure, though.
THAT Christine is, once again, available after the 3Dazer. She is in the Dark Order Shrine, but keep in mind that you MUST get the key to that shrine DURING the 3Dazer. The key is gotten from a woman in Babo'Komo, the tiny village near the Coliseum, and she mysteriously disappears after the 3Dazer! When you enter the shrine, you must first go and defeat Nankcho Nanhga and get the Apartments Key on his desk. Then you must go to the west side of the "apartments" area (the two areas to the north of the entrance with the locked doors), and enter the room furthest to the right.
Then you have to talk to the hooded figure with Coryool in your party, and he will snap Christine out of her brainwashed state and get her to come with you! Then you take her back to the House of Pleasure and talk to the lady that gave you the quest. After that, talk to Christine again, and she will give you the key to that locked chest, which contains a unique accessory. Hope this helps!