The yellow eyes were a dead giveaway and Lydia was too surprised by them to stop the baby from shoving her finger in her mouth. At least she didn't have teeth yet. "She's cute," she said, giving Derek a shrug.
Plus, she was fascinated by the ease with which he was taking care of a baby. It was a whole new side of him that she had never seen before or guessed even existed. It was certainly more interesting than listening to Scott and Stiles bicker over the best way to go after the Desert Wolf.