Hermione followed Ron's directive that she have a seat. When he spoke the words that Harry was dead she called him a liar and a few other choice words. Surely this was just a ploy, something to do with his investigation. Harry couldn't be dead, he wouldn't leave them like that. Someone had used polyjuice potion and it simply just hadn't worn off. Besides, Harry had survived the killing curse twice before.
Ron let her rant before giving her a few more details. There had been blood and the killing curse didn't leave blood. Harry had definitely been murdered and Neville was working the case. It was all he could say because it was all he knew.