In paragraph #36 of my walkthrough for chapter 11 it says this:
36. Part way up the stairs you pass through a trap and lose HP and are afflicted with pox. You find Desef about to sacrifice Wendala. You are given the choice of either Random or Luci talking to him. It doesn’t make any difference to the outcome which you chose. Desef invites you to join with him. Say no and fight him. He is joined by 2 Caul. Quest complete. You can chose either 2HP or 2ST; I had Kratin in my party and was given the choice of 3HP, 4ST or 6RS. On the way down jump to the ledge with the sleeping girl. It’s Clarine. Go up just inside the right edge of the lava flow and then left into a secret room. Clarine knows the code for the chest which has the Orb of the Depths. Jump back onto the stairs, go down and exit. You are back in the Undead Guild.
As you can see, I chose to say 'No'. My memory is that if you say 'Yes' you do get her back, but I now cannot remember how or when. However, if you search the LF3 thread using Desef as the search term you may find what you are looking for.