In every aspect of her life, Lily had always been second to her sister. Petunia was the normal one. The pretty one. The lovable one. While, in her own way, Lily was the gentle, silent one. She was born second and she'd stayed second. To Petunia but to Mary, too. It was different of course. Because what she did out of duty for her sister, she did it for love for her best friend.
But Lily isn't the kind soul she'd like to pretend to be. James loved her first. Since they first met when they started school, he was always by her side, desesperately trying to get her attention. She was eleven, then, and had absolutely no time for such a silly boy. So she ignored him. She didn't need him when she had Severus and Mary. Others came along like Remus and Pandora. Severus left.
When they were sixteen, James seemingly gave up on her. A few months later, he was dating Mary.
This inexplicably made Lily boil with rage. For days, she couldn't sleep. She screwed up so bad at practices that Dorcas yelled at her. It was terrible. And the worst thing was, she didn't know why she acted like this. She didn't care for James. She never saw him as anything else than a friend.