Harry seized upon the olive branch, if that's what she was offering. "I acted like the farthest thing from an adult in our last encounter, so for what it's worth.... I'm sorry." He was careful to remind himself that he was only apologizing for his abhorrent behavior towards her and the others in that conference room, not for sticking up for Snape – though from how he had hurt this good woman before him, he felt like he should be apologizing for that too.