is petunia dursley a squib?

[iwishiwerehermione]

No: HPFGUIDX 44590

A point I think some people have missed, or at least something I've 
never seen questioned -- Is Petunia Dursley not a muggle, but a 
squib??

Reasoning: In the wizarding world, "pure blood" wizards seem to know 
who the other pure blooded wizarding families are. Draco Malfoy seems 
to be an expert on the subject. Yet, there has never been any 
reference to Harry as a mudblood. It seems to me that Malfoy would 
enjoy insulting Harry in such a mean way, yet he targets Hermione 
instead. 

In addition there is much speculation that Lily could be Dumbledore's 
granddaughter. If this is the case, why does everyone assume Petunia 
Dursley, Lily's sister, to be a muggle? 

It would also account for Petunia's jealousy and dislike of her 
sister. It is not a form of discrimination  passed to her by Lily and 
Petunia's parents since it is clear in the Philosopher's Stone ("so 
we've got a witch in the family") that Petunia and Lily's parents 
were pleased with Lily's magical abilities. 

Perhaps instead of like Argus Filch, who lives on the edge of the 
wizarding world and longs to be a part of it, Petunia has rejected 
the magical world entirely as a means to cope with her lack of 
magical ability?

If we accept that JKR's intention was to establish what "the worst 
kind of muggles" (Philosopher's Stone) should be through the 
Dursleys, then we must reject the idea that Lily is related to 
Dumbledore and instead consider her to be, like Hermione, a gifted 
muggle.