Mystery Mother (Replica 8)
Description pulled from GoodReads:

Amy knows Nancy isn't her birth mother, but she has raised Amy as her own daughter. Then a woman shows up claiming to be Amy's biological mother. She's got her own explanations about Amy's special abilities and wants Amy back. With doubts about her identity, Amy begins to dig deeper into her origins. But the truth could destroy the only family she's ever known. Television rights optioned by Columbia TriStar.
Identity (Philosophical concept), Fiction, Middle School, Science Fiction, Thriller
Marilyn Kaye