Harry met Hermione's eye and it was that moment she knew he wasn't going to defend her. Part of it was because he knew Ron would just go on and on about it, so it wasn't worth defending the Witch. He also slightly agreed with Ron and that's why Hermione knew not to trust either of them, she knew even hoping Harry would defend her was a waste of time. She moved her eyes back to Ron and shook her head as she stood up.