The Secret of the Stone Circle — Judith Silverthorne

Twelve-year-old Emily wants to trace her family's roots and get to know her father, David, again. She even wonders if she can help her parents get back together. Something leads her to take along a 700-year-old mirror, inherited from her grandmother. A face appears in the mirror&woman from the time the mirror was made. She asks Emily to find her lost child. Emily soon discovers that she's related to many in the village. She finds the house her great-grandparents lived in, and learns why they came to Canada. But she's no closer to finding the lost child. The mirror helps Emily travel in time, to an ancient battle at the stone circle of Aikey Brae. As warriors with claymores slay people all around her, she helps save the life of Kiresz, a child who will grow up to be one of her ancestors.

She also understands that her parents won't get back together, but both of them will continue to love her.