OotP spoilers: Petunia

[Helen]

No: HPFGUIDX 62309

As I mentioned in my other post, I have tried to wade through the 
posts since OotP came out, but have not got through all of them yet, 
so I'm sorry if I repeat something someone else has said

*SPOILERS*
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Karen, Nikki, and others have pointed out that Petunia seems to know 
more than we would expect, given her hatred of magic, and I do find 
this particularly interesting. Personally, I don't think that Petunia 
could ever have been a Hogwarts student, even if Dumbledore does know 
her on a first-name basis. There are also many theories about Petunia 
being the person JKR was referring to when she mentioned that some 
one hasn't used magic yet but will use it in books to come. I can't 
really see Petunia developing magical powers, though there are not 
many people in the books who have never used magic, so I suppose she 
could be. However, I am intrigued about the back-story here. 

My pet theory is that Petunia actually grew up really liking the idea 
of magic, from stories and films etc, and one of the reasons she is 
so bitter about her sister is because Lily got the opportunity of 
having what Petunia had always wanted. I do not know if we've been 
told which of the two was older, but I always see Petunia as the 
older sister, who could not bear her younger sister having such a 
wonderful gift, and being part of such an amazing world, when she, 
Petunia, could never really gain access to it – she would only ever 
see it as a visitor. I could certainly understand her feelings, if 
this were the case – I'm quite bitter about not getting to live in 
the wizarding world as it is, if my younger sister suddenly got 
whisked into it, I know I'd be less than happy!

Does anyone else have any theories on Petunia's back-story?

~ Helen