"You didn't know anything," Hermione countered. "Just because it wasn't the killing curse doesn't mean it couldn't have gone that way!"
She was not at all interested in reasons, excuses or whatever else they were going to try and come up with. What Ron had done was completely risky and he was just lucky things hadn't ended up worse. At this point, she didn't know which would bother her more, the idea of both of them really thinking that there was nothing wrong with what had happened, or the fact that they did know and they were just teaming up against her.
"You're both completely and utterly ridiculous!"
That was Hermione's last statement before she stormed out of the room, pausing outside in the hallway and bursting into tears.