There are two versions of the novel. The first, she fell down the ladder while changing light bulbs, and the second, she was hit by a car. In both cases, it's only her spirit that traveled through time. The author made no indications on the whereabouts of the original owner of her body. Maybe she died. Maybe she exchanged bodies with the main character (now that would be a fun fanfic story to read), time-traveling to the present.