It wasn't fair, it was never fair and never had been. Her sister, Lily had everything. Their parent's love, magic powers. Lily was smart, she was pretty and had beautiful red hair. Then she met that Snape boy. Petunia had seen him lurking around for ages.
All mysterious, dressed in his odd clothes.
Petunia couldn't help but imagine what it would be like to talk to him. He'd been watching them for ages, and she couldn't help think that it was because he liked her. After all, he was always staring at the both of them, and whenever Petunia caught his gaze, he would turn away. It was only logical for her to think he liked her best.
It became something of a fantasy for her. Finally, someone who liked her better than her sister. Petunia loved her sister yes, but the spotlight was always on her. If she made friends with that boy, perhaps it could change. They could be friends, he would like her more than Lily.
Then came that day when he finally stepped out of the shadows. He didn't spare her a second glance. He only had eyes for her sickeningly pretty sister. It would always be that way, and it wasn't fair.