Some people were saying that she was stalking him. But Lily Evans was quick to deny that allegation. All she was doing was trying to figure something out.
Lily had always suspected that there was something about James Potter that he failed to show her. And if he only acted like a slightly stupid 12 year old around her, she'd just need to see him not around her. And so she set out to learn about James Potter.
She saw when he accidentally knocked over a second year and sent the boys papers flying. He apologized a million times while he pulled out his wand and fixed everything for the kid.
She saw when he'd stay after class sometimes to help a professor clean up after a messy class, or if he just thought they looked tired and might need some help and sometimes even, advice.
She saw him teach people how to do the spells then wouldn't complain when they took the credit and showed off in class.
She saw him run out of the common room the minute he heard one of his friends was in the hospital wing, no matter what he was doing. He'd even spend days by their side if they were hurt bad enough.
She saw him back up any Gryffindor he found in trouble, even if he'd never met them or was outnumbered. He'd even take the blame for these unfortunate occurrences if the teachers found out.
She saw his face light up after a successful match, in what Lily might've once thought was smug pride, but now saw to be unadulterated happiness.
It was when she saw him comforting a crying third year girl he'd seen alone in the halls when she knew. This was James Potter. This was him when he wasn't trying to win her affections, but had no idea how to go about it. This was the person that his friends saw. And Lily Evans loved what she saw.