Interesting - I hadn't noticed the connection, but it is after the attack that the Order is at the house, and Tonks notices how overly clean the kitchen is, and her mother is very tidy. And Harry wasn't the one doing the cleaning then, either, as he'd been locked in his room. Good mood piece, especially as she does know quite a bit more about the magical world than we knew at that time.
Author's Response: Thank you! When I noticed the connection, it creeped me out. I never thought, when I first read PS way back then, that I could ever feel sorry for Petunia... But it's true. Germs, one can fight.