It is posible that Lucien killed her if you are at the end of the game. Try this: press START select Map, Quest, and Family, if there is no option listed, they are gone. There are many causes.
1) She was unhappy and left you.
2) The glitch in the game erased her (Happens with a few NPCs)
3) If you finished the game, you didn't chose 'Love' when you killed Lucien.