[What's she going to do? She's going to give him a Look and frown, most of that going right over her head. None of what he's saying is making sense, except...]

Why would they do that? If shattering the crystals means everyone would die, they would die too. [Her eyes narrow.] Are you sure that's the whole story?

[If it's "what he's heard" then there's no backing it up. For all she knows, he heard the wrong story!]