Hermione knew that Ron was never really the same after Fred died. He was also angry about her rejection. But no matter, she resented the fact that he had made her the target of his jokes and had somehow rallied other eighth year boys to do the same. At first, it was just Seamus and Dean, but then Justin-Finch Fletchley, Zacharias Smith, and Ernie Macmillan also joined in on casting various spells directed at her. They would all cover for one another too, so she could never quite tell who was responsible. For a reason Hermione couldn’t fathom, the boys thought that her refusal to sleep with Ron was hilarious. She never thought that Hufflepuffs could be mean, so it was more likely that Ron and Seamus were the ring leaders. The others just pulled the pranks to make Ron laugh. Neville, out of the goodness of his heart, had even tried to intervene once, telling Ron to give it up, but Ron had basically brushed him off and denied he was doing anything to truly bother her. It was all a "bit of fun,’ supposedly.