Tenho certeza que é Um sussurro do tempo (1994) por Paula E. Downing.
A partir da descrição em Goodreads :
She was found alone lost in the stately ruins of an alien city. And when they hunted for the child's people, and found no clue that would lead them to the truth, they adopted her as humanity's first alien. Medoret grows up with the archaeologist who discovered her in her alien city, but dreams of her early years plague her, and as her curiosity grows, she begins to study the glyphs that were once carved into the stones of the alien ruins. Many mysteries of the alien land were waiting to be solved, and Medoret was determined to unravel every last one.
