Were Archer less prepared for hostility, he might have been mildly hurt by Isobel's response. It implied that he was worrying over trivial things, or possibly just being a baby. But he knew that he wasn't. He knew what was happening, and he had to stop it.
As she left the kitchen, he followed her. Luther's comment was a bit biting, but he didn't flinch at it. It was the truth. And really, weren't they just here because the truth needed to be told? "Before, you weren't losing weight. And vomiting. And visiting me at four o'clock in the morning." He frowned. "You're traumatized, Isobel. And you need help. I know that I can't give it to you, but I can take you somewhere and introduce you to people that can."