Oh, my!! It's probably a good thing that Dumbles doesn't know of her abilities or too much of her correspondence (I assume she's taking proper disposal precautions - like reducing the letters down to constituent particles after she's memorized them - I'd love to see even the most powerful wizard or witch reconstitute those). I suspect that this chapter, while calm in itself, is setting up certain matters for action later on; ghod have mercy on the souls of anyone who tries to greviously assault Hermione, I would not be at all surprised to find out that Harry has some "overwatch" charms looking out for her.