Disclaimer: It wasn't my idea. Any of it. Nor am I getting paid for it.
Crush
The first time Lily turned down a date with Roger Cunningham she didn't think much of it. Sure, Roger was rather good-looking, and she liked him well enough, but perhaps she just hadn't wanted to go out that weekend. When she turned down George Davies, though, and then Christopher Brown, she began to wonder what was going on with her. What she came up with was frightening, and more than a little embarrassing.
It was his fault, she fumed. Now that they were friends, she'd been forced to see more about James than the potential she'd always seen and he'd begun to realize. She noticed how he was always around whenever she was upset. And he knew exactly what to do, too! He let her rant without judgment, and then when she'd yelled herself hoarse or broken down in tears he'd be ready with a hand on the shoulder and a kind word. He sang to himself when he thought no one was around: he had a very pleasant voice, she thought…URGH! And most of his pranks were directed towards people they suspected of Dark leanings. It was a grim day the day Lily realized they always had been. He made her laugh without being clownish. And it was adorable how he'd turned faintly pink that time she'd observed he was a lot cooler than he used to be.
Her resistance was crumbling fast now, Lily knew. The blockade she'd had against those other things about James was all but gone. He was actually quite tall now, and his eyes glinted when he smiled. Lily had always tried very hard to ignore how attractive James Potter was. Now when he was no longer a complete moron it was nigh impossible. Her insides had started turning cold, hot, and then cold again when he smiled at her: that smile she suspected was just for her. Her thoughts drifted to him every ten minutes or so, then every five minutes or so. She began dreaming about him every so often: dreams of whispered words and calloused hands and stolen kisses.
Of course she raged at herself for it. She called herself twelve kinds of idiot for fancying James now. Now! He hadn't asked her out for ages! He'd probably lost interest. Even if he hadn't, and asked her out, she'd look like a total fool if she said yes now! She warned herself away from James. She swore desperate oaths. She would not fall for him! She had not! She was sure he no longer fancied her, and by Merlin she did not fancy him! Of course in the end it was useless. Against the inexorable power of a crush there is only so much that can be done, and eventually Lily stopped fighting it.
After all, she reasoned to herself, if she wasn't dating Cunningham, or Davies, or Brown, at least James wasn't dating anyone either. They were still friends. They had been friends a couple months now. Anything could still happen. At least he still liked her after over five hundred rejections. He wouldn't spend all the time he spent with her with someone he disliked. Head duties only stretched so far. And if he liked her…Lily could work with that.