Harry's summer in the 6th book

[vmonte]

No: HPFGUIDX 100968

Now Phil chimes in:
I love your theory, bowlwoman,
but two things came to me when reading it.
1. There is a house available, number twelve, Grimmauld Place, which
Petunia could possibly inherit, that is until Harry comes of age.

vmonte responds:

Good point!  If anyone can make that house clean, Petunia can.

Obssesive cleaning is a sign of compulsive behavior (in almost every 
book someone mentions how clean her house is). In OOTP Tonks says 
that the cleanliness is unnatural:

Page 51 OOTP, U.S. version: She followed Harry back into the hall and 
up the stairs, looking around with much curiosity and 
interest. "Funny place," she said, "it's a bit too clean, d'you know 
what I mean? Bit unnatural." 

People with obsessive behaviors are often people who feel that they 
have no control over their lives (she cannot control Harry and the 
wizarding world, and she is bitter about it).