Stranger With My Face — Lois Duncan

Laurie Stratton finally has everything a sixteen-year-old could ever want. But just as her perfect summer comes to a close, things start to unravel when her boyfriend insists he saw her out with another guy-when Laurie was really home sick! More mysterious sightings convince Laurie someone very real is out there, watching her. . . .

The truth reveals a long-lost sister who has spent the years growing bitter and dangerous. She has learned how to haunt Laurie, but the visits soon become perilous. She wants something from Laurie-her life!