"Yeah, very funny," Ron said and gave her a look. "They loved me actually. All I had to do was tell them about the time I drove a flying car, and that was it. I was a hit." His smile afterward, however, suggested that he was joking too.
He watched her face closely so as to not miss her reaction. He wasn't sure why this was so important to him. Perhaps they had just been having a bit of a tough time lately, and he wanted to make sure she was alright with him. But they'd had loads of arguments in the past, and Ron hadn't ever felt the need to get back into her good graces with a gift. Or perhaps it was the gift itself that worried him.
There was a relieved smile when she asked him to help her with it. He immediately stood and took both ends of the necklace, taking his time with the clasp and lingering over her even after he'd gotten it fastened. Then, he placed a soft kiss on the exposed part of her neck and said, "Happy Christmas, Hermione."