Hermione had been keeping an eye on Ron at the chess board. He looked as if he was going to blow at any moment, and she knew that Ginny going over there to push him was a truly bad idea. After excusing herself from her conversation with Molly, she stepped closer. It was eavesdropping, but she felt it was justified when she heard Ginny's comment that set Ron off. A deep frown crossed her features, and she stepped over as Ron stomped off.
"What Ron and I do in our bedroom is none of your God damn business, Ginevra Weasley." She said, her voice sounding cold and angry, but still dangerously quiet. Why did Ginny have to poke Ron where it so obviously hurt him? Ron was upset and rightfully so--that didn't give GInny the right to stab him.
"Just because you feel the need to broadcast your sex life in front of God and everyone else doesn't mean the rest of us do." She paused, very briefly. "Congratulations again." She added. It wasn't sarcastic or angry. She was hoping to show that even though she and Ron were angry--more Ron than she, and for different reasons--they would still be there to support Harry and Ginny. Just not right at this moment. Besides, Ginny had a room full of well wishers. She obviously didn't need Ron and Hermione if she was so willing to lash out at them. Well, at Ron.
And Hermione turned before Ginny could say anything else, and jogged off after Ron. He didn't stop when she called out to him, so she quickened her pace to catch up once he was out of the gate.