Thanks for clarifying. I agree there are other possible explanations, but I see evidence in the text for Petunia's narcissism that you don't see. I've shared the theory and evidence I wanted to share so I understand if further argument is not worthwhile. My confidence in my own sanity decreases as this discussion continues. Plunging ahead regardless:

In "Status Differential" (Ch.36), there's more evidence that Harry's parents pushed Harry to be a prodigy for their own (narcissistic) validation:

"...his own father had always done everything he could to support Harry's development as a prodigy and always encouraged him to reach higher and never belittled a single one of his accomplishments..." ""Hermione has always been quite good in school," said Dr. Leo Granger in a satisfied tone. "Harry competes at the national level!" said Professor Michael Verres-Evans. "Dear!" said Petunia.

Here, Harry's parents want Harry to be a prodigy - specifically, better than others - while Hermione's parents care about Hermione regardless of her achievements. Hermione says her parents "don't know that [she is a prodigy], and (Harry will) never be able to tell them, but they love (her) anyway."

Harry's mother's letter of consolation talks only about her needs (for Harry to survive because Harry owes it to her), not about Harry's needs.

The happy thought refers to Harry's father, not Petunia.

Harry challenges his parents only to protect them and their connection to him (e.g. after the Troll Incident) but recognizes their dominance in other situations (early chapters).

I'm still not sure what to make of the "nope", because it doesn't say why or what part of the theory is wrong. Additionally, it's possible (though somewhat unlikely) that the author is basing Petunia on a real person whose narcissism he does not recognize. This seems like a "don't poke the sleeping bear" situation.