Help! Slayer trophy will *not* unlock!

This is driving me crazy, and it's one of my four last trophies to get, the other three of which I will get on my next playthrough.
 
The Slayer trophy...  I go to the lady, use the "persuade" option with her, succeed, kill the elves, and... nothing.  Quest Completed, yes, game progresses, yes, but trophy unlock?  No.  
 
I talk to the werewolf by the entrance to the forest afterward and still nothing.  This really bugging me because after my next playthrough this will be the only thing preventing me from getting the platinum trophy