Fleur had noticed it a few weeks after she arrived - how odd Professor Moody was. She had brought it up to Hermione and with a few carefully placed words and gestures, the truth had been brought to light. Realistically, they knew that they should have told Dumbledore but after the fiasco with Gabrielle, neither of them were inclined to do so. Besides, it worked well into their plans for Dumbledore - undermining him was the first thing that they had done.