Cloud City (Anna Strong Chronicles #8.5)

Vampire Anna Strong never expected to find the witch Sophie Deveraux on her doorstep, asking for a favor. But Sophie needs help, even if it's from the vampire who killed her sister. Anna, driven both by guilt and obligation, agrees to help Sophie and her psychic alter-ego Jonathan. So begins an adventure that takes them to Leadville, Colorado. All too soon, Anna wonders whether Sophie is truly a victim of circumstance . . . or the author of a clever plot to rid herself of her unwanted psychic twin.