"How can you just act like we were never friends?" Snape hisses. "How can you forget five years because of one stupid mistake -"
"It wasn't stupid!" Lily rounds, nearly colliding with Snape, who was still pursuing her down the empty corridor. "Calling someone fat, or ugly, or wishing they would fall off the astronomy tower and die is saying something stupid. What you said to me was-" she stops abruptly. In the torchlight, Snape can see a thick, shimmering glaze start swimming in the rims of her eyelids, brightening them red to match her hair. It comes on as sudden and unexpected as summer thunder. The tendons in Lily's neck work furiously to help her speak, but her lips defy the effort and stay clamped shut for entire minutes. She stares at the ground between them as if she'd watched something vanish there a moment before.
(She still hasn't looked at him – really looked at him in the eyes – not once, since that day. It's gradually driving him mad.)
"A mistake, you said." Lily's voice comes back to her raw. "I wished it was."
"Lily, please. I was… I was humiliated and - and Potter," he spat, "Potter, he-"
"Don't blame James," Lily cuts him off, cold. "All you ever do is blame other people, Sev. It's spineless of you."
"Fine! Forgive me for assuming you'd want to make it all about him, you usually do these days!" Snape snaps, even though he knows he's inflicting his own wounds now. He can't help it. White anger is coiling in his guts, driving him closer to saying even more he'll regret. If it's not about Potter, then why are you always next to him now? Why are you always smiling and fucking laughing around him like he's something I never fucking was or could have been? Why are you, when I know I could-
"No," Lily says. "No, it's not fine at all." There's something new beneath the anger that's become so familiar to him. It makes Snape cold. "Do you think I didn't want to forgive you?" Lily asks quietly, all the heat seeped out of her anger like ice applied to a burn. "You were my best friend, Sev. You think I didn't try to write it off as a stupid mistake? Every night I tried to believe it was."
"It was, Lily. Please. Why can't you just believe that?" Snape's voice is cracking and he hates how weak it makes him sound, how pathetic. He just wants to reach out and touch her. Her hand. Her hair. Anything. If he touched her, she would have to look at him in the eye again. Then she would see him. She would feel something.
"Because, it wasn't. You said it, Severus. Even if you didn't want to say it to me, you said it. You thought it. It wasn't just a mistake."
Lily's tone stays his hands. And so he is forced to stand there, awkward, pleading silently and unable to move.
He's losing Lily Evans.
"You know, when we met you turned my entire world. No one in my family knew a whit about magic. My parents were frightened it, frightened of me, even if they tried not to let on they were. Petunia was worse – just jealous and hateful no matter what I did. And then there was you. You came into my life that summer, and you showed me what beautiful friends could be like. What beautiful magic was. Why do you think I focused in charms anyway? Maybe I had a knack for it but it was also because… I loved the ones you used to cast for me in that garden."
Severus was aching with the memories of it. He'd never thought Lily held that summer before Hogwarts so close to her heart, as he had. He'd never imagined those sentiments ran so deep in her, as they had for him. And maybe not everything was lost, he thought, desperate. Maybe -
"I really loved that boy. I know you could be a good person, Severus. I know better than anyone. But," Lily looks up, looks him in the eye for the first time since that day at the lake. They are bright green and bone dry. They rip through him. "But the things you're doing, the side you're choosing… it's wrong, Sev. It's wrong. And I can't make excuses for you anymore."
"Lily." He feels like he's fucking drowning. He reaches for her hand but his limbs are too thin to even move through the air between them.
"If I ever see you again, and you're still standing on that side – I'll fucking stop you myself."
And with that, Lily turns on her heel in the corridor. And then she is walking away from him, to where he cannot follow. And then she is gone.
A/N: Because James/Lily is my OTP, but I'm sick of so many peeps writing Snape out as a flat-as-fuck, uninteresting piece of Satan-spawn character in their fics. He was deeply flawed, an anti-hero, right up until the end. And he arguably underwent the most (interesting) growth over the course of his story.