Toby Whithouse originally conceived the show as a drama in the vein of This Life (1996) with the three characters sharing a flat. Originally, Mitchell (Aidan Turner) was a sex addict, George (Russell Tovey) had anger-management problems and Annie (Lenora Crichlow) was an agoraphobe. Whithouse added the supernatural elements later, finding what he believed to be the underworld equivalent for each character: the sex addict Mitchell became a vampire, the angry man George became a werewolf, and the agoraphobe Annie became a ghost.
Annie's headstone changes from season 1-2. The first time she views it, it reads "beloved fiancée.." In season 2 when her mother is viewing it, it simply states her name. Unless of course her family had it changed when Owen confessed to killing her, but they never mention it.