Kathy is a soul living in a human host. She becomes Wanderer's Comforter( the soul equivalent of a therapist) to help her deal with her tricky new host- Melanie. Kathy chose to keep her host's name because she was apart of the first wave of souls to occupy the planet, meaning her host's consciousness probably faded away, as the humans who were taken by surprise did not fight back. Kathy had to pretend to be her host for several years, so humans would not know that the souls had arrived. Even after the occupation was pretty much complete, she kept the name Kathy and stayed with the soul who occupied her host's spouse's body, Curt.