Written for my wonderful friend, dreamsofcrimson. Sorry it's so short.
He shouldn't still love her—he knows this full well. Severus has analyzed the situation thoroughly and come to the rational conclusion that to love someone as stubborn and blind as her is pointless. She closes her ears to the things she doesn't want to hear, and she clings to that one thoughtless moment as her excuse. Lily Evans is stupid and shallow and stubborn and…and bull-headed…and…
And he still loves her, dammit.
Because all of his cool intellectual reasoning can't stand up to the irrational, iron-clad folly of his own heart. The mind that he took so long to train and make sharp begins to stutter and fail when he catches sight of her verdant eyes. Her long red hair turns to fire as the sun runs through it like watered-down honey, and the list of reasons for him to keep walking dissolves. She smiles, and now the well-oiled machine of him is coughing out black smoke as he comes to a full stop, only just holding back from running to her.
And then James Potter appears from behind, wrapping his arms around her waist, pressing his face into the curve of her neck, making her laugh—
Dammit, dammit, dammit!
Snape's brain kicks into high gear, driving him far and away down the halls before that damned inconvenient heart of his can cause any more trouble.
Beauty is a stupid reason to keep loving someone, he seethes, face set into that familiar, guarded scowl that has served him so well. But it's not just because she has a pretty face, and Snape knows that. It's because she glows from the inside out with her real beauty. She is the kind of person who has never thought to hurt others or let the weak suffer. She draws in those around her and infects them with her light. She even managed to change that git Potter, for Merlin's sake! Ever since she gave in to his flirting, he and his gang laid off on their assaults until finally they stopped altogether. The former bully even seems embarrassed in the rare instances when they encounter each other. She loves equally and unconditionally and without inhibitions.
Except…except when it comes to him.
For him, there is only that sad, bewildered look and the tightening of her lips. For him, the face that used to shine for him in a way it did for no else now shines on all but him. For that one mistake—that one thoughtless, defensive, lashing-out—she has sealed herself away from him forever. When they accidentally catch each other's eyes, her gaze grow dark, as if she doesn't recognize the person she sees anymore.
(Sometimes, in the middle of the night, with nothing but the sounds of his own breathing and the covers pulled up to his chin, he wonders is she's right. If with all the strangling of his heart and the devotion to the all the things that Lily hates, maybe the person he used to be wouldn't recognize himself either.)
Lily Evans looks up casually, the laughter gradually fading from her throat, and her eyes catch on the all-too-familiar swish of a black cloak and the flash of cold, dark eyes. Her smile falters and grows stiff; her heart sinks down into her stomach. She wonders if he even noticed her, if he even deigned to glance her way. He still hasn't forgiven me, she thinks. For that one moment of childish anger. She was full of the hot, boiling venom of indignation, and she wouldn't listen to the things he tried to say. She still feels regret for the way it happened, but deep inside she realizes that the thoughtless moments are when you see the real heart of a person. He thoughtlessly called her Mudblood, and in some ways she wasn't able to forgive him for that. Maybe it's shallow and maybe it's silly, but to hear that one word—thrown at her so many times from unfriendly mouths and mocking faces—slip from the single person she thought would never judge her was what hurt the most. To hear it come from him.
And now every time she sees him, his eyes are as hard as lead, his face wiped clean of any emotion. He easily stands next to the people who represent all that it wrong in the world; he laughs at their cruel jokes and sneers at those that she loves. He isn't the boy she once knew. He has chosen his side, and by some heartbreaking turn of events it isn't the one she's on.
Every now and then, their eyes meet, and she wonders into what kind of darkness her friend has gone.
"Everything alright, Lily?"
She blinks slowly, turning her face up to James'. She stares at him for a moment, unreadable.
No.
"Yeah. Just thinking."
Snape turns the corner, leaving the sunlight and the sound of her laughter behind.
Still loving her, of course.