"We’ll give you enough calming and sleep potions to hopefully prevent you from scratching at it. Have you remembered anything else since our last meeting?" McGonagall upon learning what had transpired at the mansion ordered her to speak to Madam Pomfrey at least weekly. From what she knows, Madam Pomfrey doesn’t tell McGonagall anything Hermione confides. As such, she’s probably the person who knows the most about Hermione. Including the blank spots in her memory. Pomfrey assures her it’s likely because Hermione passed out due to pain. She says it’s a mercy, that Hermione probably escaped some of the pain.