Nimue winced when she realized Mordred was talking about the 'parents' she had taken him from. Comparing her to them. She hadn't wanted to be like that. She'd wanted to give him another chance. She'd wanted to help him learn to be a productive member of this society. But she hadn't. She'd failed him. She couldn't deny it.
Part of her wanted to do better by him, but part of her knew she couldn't. Maybe he hadn't set this fire, but there was no guarantee he wouldn't set the next one. She couldn't trust him. Even if she had proof Mordred had nothing to do with this fire, she wouldn't be able to trust him. Nimue hadn't trusted Mordred for months.
She felt guilty, but he was right. She wasn't going to go back for him. It was terrible of her, but she couldn't love the boy. She couldn't even do right by him. She had no answer for him.
Nimue was surprised the guards hadn't tried to put out the fire on their own, despite lack of training or equipment. Normally she found their bravado obnoxious, but she was grateful for them now.