They’d sent the lady with the pointy hat to explain, but Petunia would have none of it: she didn’t want to be unusual, she didn’t want to have to lie to everyone about where she went to school, and she certainly didn’t want to lose the friends she’d worked so hard to keep in the Juniors.
When she refused to go, the lady and even her parents tried to reason with her, but Petunia’s mind was firm, and nobody could ever dissuade her when she had made a decision. The lady left them with a worried expression and instructions for her parents on what to do if Petunia ever “lost control” of her “magic” – but there was no need. The very idea of losing control of anything went against everything Petunia had already worked out about herself at the age of eleven.
When Lily got her letter two years later, and when she returned from her first term away with countless unbelievable stories, Petunia refused to entertain the idea that she might regret her decision; when she asked Lily for more stories about Hogwarts, it was merely to confirm that she would have hated it there; when she dreamt of carefree children flying around on broomsticks, she managed to convince herself of the unpleasantness of the experience. There would be no magic in her world, if she could help it.