Hermione notices that squirming from Jamie, but she says nothing on it. He likely knows just how foolish his move had been, and so she certainly isn't about to rub it in. It wouldn't help anyone, and would only succeed in alienating him.

"I understand why you thought you were doing the right thing, Jamie, but fiddling with one's past can be incredibly dangerous. Fiddling with the past of subsequent millions of people is another thing entirely." Of course, he doesn't need to hear that; it just bears saying. The more important thing, in this case, is in what he said last.

"What did it end up doing to you?"