While I have not tried searching for her yet myself, I have heard that several others who have completed all 3 storylines are also unable to find her. Perhaps this is related to the issue where random encounters don't seem to be occurring in the higher chapters. (I'm not sure if that has been fixed or anything, though)
Edit: Okay, so I finished restatting and started searching, and I found her. I couldn't find her a second time, with ~35 more searches.