She makes sure the diamond is large enough to contain a man. It’s a foolish thing to be doing, not least because she knows she’ll feel silly when the devil inevitably fails to be summoned, but it’s not as though she has anything better to do with her nights. Hermione has no friends and never has. Something about her intensity, her intelligence and aggressiveness, repel people like a bad smell. She’s long since given up hope on finding someone who isn’t eventually scared away by her relentless drive for more: more knowledge, more organisation, more perfection.