She is studying. No one dares to interrupt her while studying. Except for him.
He doesn't care or doesn't even realize. He just runs up to her, to the table in the most quiet corner of the room and starts to talk. Not with her. He talks at her.
He spills the words between her and the book so that she cannot see the letters anymore and has to put the book down and has to listen.
Hermione needs someone to interrupt her while studying but only her and Ron know that. And they agreed silently not to tell anyone.