Oh absolutely I always believed that Twilight ripped off TVD a bit, LJ Smith said that when her books were re-released a lot of SM fans were contacting her to complain that she ripped off Twilight and she would always respond by telling them to check the copyright dates :P

And I suppose it is possible that Kelley Armstrong did read TvD, I remember that Stolen had Elena reference Buffy The Vampire Slayer and season 4 which always made me smile heh, so she could well have been following vampire lit as well. Still the most we can say is that she may have been inspired by the name Elena, otherwise they don't have much in common really