Lily Evans took pride in her ability to control her emotions. Sometimes however, she slipped up. When she slipped up beside the lake, she thought she caught herself before anyone else did. When James Potter lifted Severus into the air by the lake, Lily couldn't deny that she almost smiled. She felt the right corner of her mouth twitch upwards, but she deliberately frowned instead.
She knew why she almost smiled. Severus had been bothering her lately. She knew that he was hanging around with the likes of the baby Death Eaters. She knew that had she not been Lily that Snape would have harassed her cruelly and treated her icily as he did to every other Muggle-born in the school. So to see James Potter take his power, was almost amusing.
Then she realized, she needed to be firm in her stance. James Potter should not be treating anyone this way. He was absolute trash, and to have smiled at his antics only would have encouraged him. She knew that James Potter wanted to date her, and that he was endlessly trying to impress her. The most impressive thing he had done as of late was not burn anyone's OWL to ashes for any subject.
Lily was very conflicted- dare she show any sign of happiness for the retribution that Severus was receiving and give Potter some positive reinforcement or should she remain concretely rooted in her defense of Severus Snape, blood supremacist and future Death Eater? She chose the latter, as she still had some type of hope that Severus might still be the little boy she met at Spinner's End.
Lily did have to admit that Snape had been a bit nasty to James. Yes, Janes had jinxed him, but to use a spell that was malicious enough to cut open Potter's face was a bit excessive. She read the incident reports later in McGonagall's office. It was confirmed that the bit of magic Snape had used was dark magic. Lily had to admit, regardless of the prat that Potter was, unnecessarily jinxing half the Hogwarts population, he fought with clean magic. None of the spells he used were harmful, and they were all rather foolish and immature.
Then, Lily realized she should have openly laughed when James hoisted Snivellus into the air, the second the first syllable of the word "Mudblood" crossed his lips. She was dying inside, as any hope of her best friend returning to her had just evaporated, but she maintained her composure, and coolly suggested that Snivellus wash his underwear.
She lost her composure when Potter commanded Snape to apologize. This was in part because any apology James elicited from him would have been insincere, and due to James Potter being an arse. So in that moment, Lily lost her temper and told James Potter exactly what she thought of him. She was already mad at Snape, so she might as well use that to fuel her honesty.
The two of them so desperately wanted her affection, but neither seemed to be able to figure out the right way to go about it. Snape simply did not have the right core values. The way he treated her shouldn't have been an exception; he should have treated all Muggle-borns the right way. She shouldn't have been the only Muggle who didn't expect hateful words to fly out of his mouth or jinxes from his wand.
James Potter might have been a kinder soul at heart, but that was clouded by his asinine behavior and his constantly trying too hard to look cool and show off for his friends. When she thought about it, James really did make her sick to her stomach. It wasn't because he was a good Quidditch player or because he was such a talented wizard. It was what he did with that recognition and notoriety. He used his cleverness to not get caught, and his charisma to get out of detention if he did. His friends constantly egged him on- Remus not so much, but Remus was a bystander- and James just let his desire to be a show-off take over. Maybe Potter did genuinely like her, but she couldn't stand to be with someone who was so arrogant and such an instigator.
Contrary to popular belief, Lily Evans did not hate James Potter. She had been known to laugh at a few of James' jokes and she didn't mind idle conversation with him and the Marauders at meatltimes. She had problems with what came after the laughter and the nice interactions in the Great Hall. James Potter always had to go to the next level, because he didn't know when enough was enough.
If Lily laughed at a joke James made about the porridge, to James the logical way to make the joke funnier and Lily laugh harder would be bewitch the porridge to pour itself onto the head of some poor unsuspecting first year. If they made chitchat in the corridors about potions homework, during class, James would say something along the lines of, "Oi! Evans! Remember when we were doing the homework together?" and then wink. It made Lily blush like nothing else, and to commit to James Potter when he would inevitably ask her out, when he so temptingly asked, "Go out with me Evans?" would be to commit to never-ending attention that she didn't desire.
She didn't realize until after she lectured James that she had drawn her wand. This was likely why James had backed down. He knew she was a ferocious dueler and though he wouldn't admit it, she could likely beat him as she had already mastered silent spell casting. She hastily stowed her wand away and after giving the boys another look of disgust, she walked away, pretending as though she had not just lost control of her emotions.
James Potter took pride in his ability to read people. What he did with that information, he was usually, but not always proud of. He knew that Peter, Remus and Sirius were good people and they were going to be his friends. He could tell that Moony and Padfoot had trauma when they met on their first train ride and he could tell that Peter was simply scared and wanted to fit in. So he made the best friends a lad could hope to have before the school year had even started. He was proud that he had been able to be a good friend to these people since they were 11 and even more proud that he had known that things would work out just fine.
In very much the same way that he read his best mates, he read Lily Evans and Severus Snape back when they were first years. He knew that Snape had been no good for the beautiful girl standing next to him. However, they were very young kids at the time and James had been unable to articulate the bad feeling he got from Severus Snape, so he did what seemed easiest, and he made fun of him. Unfortunately, James had not taken into account the way that the red-haired witch would react to his antics.
Since then, James and Severus had maintained this rivalry and James had gotten the rest of the Marauders (albeit Remus was only half-assing it) on the anti-Snape bandwagon. It continued to escalate. James was proud of his ability to read people, and he was also proud in general. He could not admit that he was wrong to harass Snape, and so he made sure to whole heartedly follow up on it as frequently as he could. This rivalry however had cost him the affection of Lily Evans. He hoped that one day he could be so suave as to have the best of both worlds. One where he would get to hex this filthy excuse of a wizard and date the girl he decided would be his wife at the age of eleven.
He loved Lily Evans, or at least he thought he did. He proudly shared this proclamation with her regularly and just as frequently received glares and snorts and narrowed eyes in response. As much as he badgered Lily, deep down he obviously respected her. She was brilliant. She could make any potion there was, her Charms were highly effective, she could transfigure damn near anything, and she knew that Remus was a werewolf, yet she still remained his friend. To top it all off, Lily Evans was a Muggle. He was very respectful of the amount of studying he knew she put in at the library and knew that she deserved the results she got.
For some reason, James never said any of that to her. Instead he would just constantly ask her out and act offended when she said no. James Potter was very intelligent when it came to deciding whether or not a person should be trusted, but sometimes, with this information, he made the wrong decision. He acted in the wrong way, in a way that made him seem like a blithering idiot.
James knew when Snape had been hoisted into the air the first time that Lily had almost creacked a smile, which she immediately turned into a frown. Regardless, this encouraged James to carry on, because she had wanted to smile. He thought he knew her better than she knew herself. He thought perhaps Lily wanted to see Snape tormented, the way he tormented other Muggles, despite being half- Muggle himself. However, James knew to back down when Lily Evans drew out her wand. He knew she could cast a fierce stunning spell that would knock him down. He had listened when she requested he let Snape down, but had also made sure to let everyone know that he still thought Snape was trash. This was confirmed when Snape called Lily Evans a Mudblood. The immense respect that James had for this girl was what caused him to become truly angry as he demanded an apology from Snape.
And then, when Lily began to shout at him, he knew every word she said was true. He did act like an idiot, his hair was always messed up, he did show off for his friends, and he knew that he made her sick. He hadn't heard her say this before and perhaps he was hurt, but he was inclined to play it off, act nonchalant, and act as though what Lily had actually said was that she wanted him. He couldn't act as though Lily Evans was right, and so he continued to bully Snape for the crowd that had gathered around. While his body was physically focused on embarrassing this budding Death Eater, he was mentally focused on the words Lily had said. His wand pointed at Snape, but his spectacled eyes were trained on Evans as she gathered her books from the lake edge and entered the castle.