She disappeared for me when I arrived during nighttime (and there was a vampire attack), but I found her in an alley just beside her normal sleeping place. The alley is just a door arch and not very deep, but she had taken cover there.
PS: If you are going to adopt her, start with purchasing everything she's got to avoid the "stuff's too heavy" bug before adopting her.
I haven't been able to find her (or Lucie) either...I've checked all the places it says she should be, watched so many video's on You Tube to get clues but after about 10 hours looking (real time not game time) still no where to be seen