Hermione knew how much they had decided to tell her, but it was impossible not to say more than she meant to with Ginny looking at her that way - and the desire to make sure that no one died in their crossfire, Hermione wasn't sure she could live with that.
"Something's going to happen at Hogwarts. Harry has to ... well, we have to come back, there's something that has to be done there and Harry's the only one who can do it. But the moment we're there, He's sure to know."