He understood a little about the allure of the darkness of magic. While even he had not gotten quite as into it as she had (grief can do so much to a person), he understood better than any of the others here would, except for the possibility of Angel. Like Willow, though, his own decent into darkness had involved a death that he felt responsible for. It may not have been as direct as her's, but he was every bit as responsible for him.
Giles wasn't sure just how much he wanted Angel around any of them, since he seems to lose his soul every time they turn around now. He would definitely research to see if it was possible to find a way to anchor it to him. There had to be a way to prevent Angel from going berserk every few years. Well, Giles had a way, but it involved a sharp, wooden object, and he'd rather avoid that, if only for Buffy's sake.
"Good luck on your next appointment, then," he said, returning her smile. He was so glad to see any of them smiling again. He sort of wondered what it was, but he didn't want to pry. He got a smile out of her, and that was more than enough for him. He was a little surprised when she kissed him on the cheek, but kept smiling at her just the same.
"I'm glad to be helpful to you," he said. He took a sip of his coffee and finished it off. "Hope you enjoy the coffee here," he said with a slight grin this time. Maybe she would eventually get used to the fact that, yes, occasionally, he did drink things other than tea.