The Persistence of Memory — Karen Ripley

Cassidy had no idea who she was or where she came from. Her earliest recollection was of meeting the people who called her a Horseman, for her ability to communicate almost telepathically with her gray mare. But they could tell her nothing about her missing memory, nor did they care. Even the community of farmers who took her in seemed to find her amnesia unremarkable. But Cassidy was plagued by a persistent, nagging doubt that the biggest part of her problem was that the world around her was not her world.

Yet when the sight of common, everyday objects -- sunglasses, a saddle, a rifle -- began to trigger a flood of partial memory, Cassidy knew that something was dreadfully wrong. Worse yet, the more she remembered, the more she was certain she had come from a different world -- a realization that threatened not only her sanity, but her very life . . .