Selina found out in Istanbul. She had been gone from Gotham for two months. She knew the second she saw the test in that precarious room in Bucharest. She also knew she couldn't tell him. Not then, as she thought he would have locked her in the manor. Wrapped her in Kevlar and bubble wrap. He would have loved you both to death, but it would have been on his terms. In his world. She couldn't... breathe in there. Not then. So she hid and let him believe she was just... gone, for sixteen years