I decided to be a vampire lord. I did all the quests and at the end in the cathedral Serena would not stop attacking her already dead father. I believe at that point she was "following me". Since then I have cured myself of vampirism and turned back into a warewolf to continue companions quests. I went back to the castle to see what would happen and I was unable to talk to any members in the castle as they all stated "Serena can turn you back into one of us." I have looked all over the castle and many other places for her yet cannot find her. It is also too late to go back to a previous save. Anyone know of any possibilities?