Irisu was quite a manipulator. He praised Oreki sufficiently so that he would completely fail to doubt her or the setting she had created. But then again, she even looks like a completely cold and merciless person and didn't bat an eyelash when Oreki accused her of only thinking of the end result and nothing else, so I doubt she gives a shit about how this might have affected Oreki. She showed some concern when chatting with his sister, but I reckon that was faked as well and only due to the fact she respects her personally and would desire respect in return. A valuable lesson for Oreki, in any case. When solving future mysteries, he will also count in factors like this, no matter how much it hurt this time.