Disclaimer: I do not own these characters, they are the property of their creators, nor am I seeking to make a profit from this.
I got this idea a few hours ago and I couldn't help myself in writing this. It's sad, sorry.
Tauriel wandered the field of victory, the rush from battle still coursing through her veins. She spotted Legolas a little ways away, helping an injured man set a broken leg. She considered going to help him, but he seemed like he was doing fine enough, and she was looking for someone. The small brown haired dwarf had captured her attention so quickly, and they confused her at first. But then she heard that he was poisoned, and the all-consuming need to help took her and before she knew it she was in Laketown chanting Elvish over him before she knew it.
She followed Legolas after the orcs and thought that would be the end, she would probably never see him again. Especially when they returned to the forest kingdom. She thought Thranduil would never let her out of the gates again, but then news came that the dwarves were successful in their endeavors, and the dragon was slain and the Mountain was once again theirs, and suddenly Tauriel, Legolas, and nearly all the elven warriors in the forest were marching to the mountain.
And then the battle. Tauriel saw Kili several times during the fight, and even fought beside him at one point, before they were separated again.
Thunder cracked over head as it began to rain, slowly at first, and steadily increasing into a torrential downpour that made the miserable feeling around the battlefield that much more unbearable. An hour passed, and then another. She saw more death than she had ever seen before that day, and it made her sadder than she had ever been.
The rain ceased, and the air felt clear. The sun was rising, and through the cries of the wounded Tauriel heard a small voice not far from her. Her head jerked to the side and she looked hard at the bodies. She recognized the small brown haired form laying twenty feet away and flew to him.
She knelt beside him, her hands hovering over his torso. He had an arrow sticking from his arm and a large gash across his chest. One of his hands clutched his stomach and the other was clasped in his brother's. A jolt of sadness went through her she saw that he was dead. And as she looked down at Kili she saw that he was not long in following him.
"Kili," she said, her voice soft and trembling. He turned his head slowly, a pained look crossing his face, and his eyes met hers.
"Am I dreaming again?" he asked, his voice barely audible. Tauriel smiled, though it didn't reach her eyes. They brimmed with tears, and she noted in the back of her mind that she could not remember crying before. She had no idea how this small dwarfling had entered her heart so quickly, but as she searched for him she stopped denying the fondness she felt for him.
She placed her long-fingered hand on his cheek, brushing away a tear that fell from his barely-open eye with her thumb. "Fili?" he asked, his grip on his brother's slack hand tightening.
"Shh. H-he has gone to the halls of your fathers," she whispered. A small cry escaped Kili, and he squeezed his eyes shut. "He will be feasting, and drinking in merriment for eternity."
"I-I'm not long there m-myself now," he said, his voice shaking. She could sense the life fading from him. The gaping wound in his chest steadily wept more of his blood onto the water and blood soaked ground, and he had not much longer. "I'm glad. . . someone so beautiful could be the last thing. . . I see. . ."
He closed his eyes and his breathing slowly evened out, as it got softer and softer. Tauriel blinked away her tears and started singing a soft lament for the dead. The corners of Kili's mouth turned up slightly just before his breathing stopped, and he was gone to join Fili, and all the others in the afterlife.