Teren does knock, but it's as she opens the door, because it's Howe, she didn't hear voices on her approach, and he's about as likely to be doing something interesting in here as she is to sing the Orlesian anthem.
...she knows better than to do this in the room he shares with Anders, at least. She's not an idiot.

"Letters," she boredly announces, coming to the desk with a stack that she's already gone through, marked, and answered. Noticing the spectacles as she turns back toward the door, Teren narrows her eyes for a brief moment, just long enough to register that something is different. However, she says nothing of them, as there'd be a definite irony in her remarking on signs that Nathaniel is aging.
"Nothing of any interest. Haven't heard a peep from that dodgy bunch in Ansburg, not that I expected it." Her words say 'I don't care', her tone says 'we should kill them before they kill us'.