The change is not subtle. Terezi notices, and it's difficult not to feel sorry for him. There's so much anger in that short sentence, so much bitterness bottled up... It's like a wave rising high up over the beach. She feels very small in comparison, and the meager "I'm sorry" that she managed to murmur is very insignificant. What can those words do in the face of this prolonged torment he's suffered? Nothing, is the answer.

It's not good enough. Nothing is going to be good enough to make this feeling go away, but Terezi turns to sniff at the area for something that might at least help. All she really smells is the honey... Which she turns to the counter and buys a large container of it. As soon as she's purchased the thing, she pushes it into the Helmsman's hands.

"Here. Just take it. For answering my questions." She can at least make that much up to him.