Hermione did not have much experience with boys or sex in general. Not before Draco became a part of her life. And Draco wasn't a boy, really. He was a young man. And he had made Hermione into a woman in many different ways. She no longer viewed herself as a girl. Many things had changed in less than a year and she couldn't imagine her life any other way. Which was why it didn't scare her of the new level of intimacy this created between her and Draco. In fact, she welcomed it after what they had just declared. This was different from when they first had sex. Or any other times they came together.