Actually, I assumed you were responding to my question on your comment! Sorry! I only realized after first posting this comment.
She thinks he's very serious and intelligent. Yvaine would return the compliment he gave her about her calmness, because she thought he'd taken things as reasonably as one could. She just didn't think of it at the time. She also wonders how much the seriousness is due to their circumstances. They do warrant that particular response. But overall Yvaine finds him mature and level-headed. If she weren't hesitant to jump to conclusions, she'd also decide he seemed wise. She definitely wouldn't mind talking to him again.