Pieces of Her von Karin Slaughter

Andrea knows everything about her mother Laura. She's knows she's spent her whole life in the town of Gullaway Island; she knows she's never kept a secret in her life. But one day, Andrea sees a different side to Laura. Now, Andrea must go on a desperate journey to follow the breadcrumbs of her mother's past. If she can't uncover the secrets hidden there, there may be no future for either of them... What if the person you thought you knew best turns out to be someone you never knew at all?