Petunia certamente crede che ci sia stato qualche favoritismo e potrei capire perché.

Spesso, quando c'è un bambino speciale in famiglia, più tempo e risorse dei genitori vanno in quel bambino speciale, intenzionalmente o meno.

Petunia guardava come i suoi genitori portavano la speciale Lily a Diagon Alley e spendevano quello che posso solo supporre essere centinaia di sterline in attrezzature speciali e strumenti che Lily avrebbe avuto bisogno nella sua nuova prestigiosa scuola. Petunia, nel frattempo, probabilmente ha ricevuto nuovi quaderni, penne, forse una nuova borsa... tutte cose abbastanza noiose rispetto a bacchette, calderoni e abiti da mago.

Ora non so se anche Petunia sia andata in un collegio. Se è andata in un collegio e lei e Lily erano in vacanza nello stesso periodo, i suoi racconti del suo tempo fuori casa erano probabilmente messi in ombra dai racconti di Lily sulle lezioni di trasfigurazione, gli esperimenti di pozioni e le partite di quidditch. Her parents probably listened in rapt attention as Lily described Hagrid or the ghosts or the talking portraits. They were probably less interested in Petunia’s exploits.

And if Petunia did go to a local school, she probably had to watch her parents fawn over Lily, who had returned after spending so long away, and then watch as they doted on her in the time that they could.

Of course this is all speculation as Petunia is the only one who speaks about Mr. and Mrs. Evans and she clearly resents them.

But if we look, then, at Petunia’s parenting style, we have some clues about how she was raised.

• Vernon and Petunia never had another child after Dudley. Now, this could be due to having unexpectedly having to raise Harry, but they clearly bought a house that would have been big enough to accommodate another child, especially if Harry was forced to sleep in the cupboard under the stairs. Why does Dudley need two bedrooms? My theory is that Petunia only ever planned to have one child because she didn’t want her children to experience the same rivalry that she and Lily experienced. Perhaps she originally intended to have one room for her and Vernon, one room for Dudley, one room for his playroom, and one room for a guestroom.
• Petunia clearly favors one child over the other. She didn’t raise Harry and Dudley as brothers…she spoiled one and mistreated the other. Was it intentional? Or was it something she had unconsciously learned from her parents when she was a child? I mean you have to be a pretty awful human being to intentionally mistreat an orphaned infant. So maybe it started out unconsciously and then grew from there?
• Petunia takes great pains to treat her muggle child better than her magical one. Is she overcompensating for her parents treating their magical child better than their muggle one?

All in all, I think there was some favoritism showed to Lily. Che sia stato intenzionale o meno, non lo sapremo mai.