Oh. That's why she'd been friendly. Anders' expression falters and he looks down at Purrelden.

"To stop a Rite of Annulment, to stop constant compromise from continuing to cost mage lives, I blew up a Chantry. Fewer died that night than otherwise would have, a few dozen versus hundreds, but they did die by my doing, my hand."

And this is probably when she walks away. She'll be far from the first. At least the conversation had been nice while it lasted.