Disclaimer: Buffy the Vampire Slayer and Lord of the Rings belong to their respective creators, Joss Whedon and J.R.R. Tolkien.
Buffy knew it annoyed Elrohir and Elladan to no end that she could tell them apart. From what she could gather, only other Elves and those who had spent considerable time with Elves could really tell the differences between the sons of Elrond, which were few to begin with, so to have this human girl they'd barely met call them by the right names each and every time drove them to distraction.
They'd tried tricking her. They'd greet her in the morning, go off, switch clothes and weapons, and greet her again in the afternoon, only to have her point out who was who with a smile. They'd tried sneaking up on her singly and in a pair, catching her by surprise, catching her alone, catching her in a hurry. They'd tried getting the other Elves to deliberately call them wrong names in her presence.
Nothing worked. Buffy always knew, and she wouldn't tell them how.
Anyway, it would have disturbed them even more to be told. A girl just didn't go around telling people that she could hear the faint irregularity of their heartbeats, see the smallest of natural variations in breathing pattern and gestures, smell the imperceptible differences in their sweat.
They were nice, Elladan and Elrohir, good people, and friendlier than anyone else in an alien place. They were always coming to look for her, talking to her, trying to teach her their language. Sometimes they were pesky, in that they absolutely refused to take her hunting, let her handle any kind of weapon, or walk over any kind of threshold or bump in the road unassisted. When she was in a mood to be vain, Buffy figured that they were using manners as an excuse to hold her hand. When she was in the mood to be a realist, the latent chauvinism infuriated her. But that didn't last - who could stay mad at those faces?
Through them, she was learning. It was a strange, strange place she'd woken up in, and she had so much she needed to know, not least how to talk to the inhabitants. The language was hard, harder than high school French had ever been, and even after months of practice, she knew she was still butchering their tongue. But Elrohir and Elladan were patient, more patient than anyone else except maybe Elrond and Arwen, and she was learning.
Eventually, she knew enough to understand some of what they said to her. Buffy understood what Glorfindel was trying to get her to do when he said, Gwanno ereb nin.
What Elrond wanted when he said, Lasto.
What Erestor wanted when he said, Sedho,
or daro i,
or ava vanta i salquesse.
What Arwen was trying to get Buffy to tell her when she said, gently, Avo acheno.
Buffy understood what Elrohir meant when he took her hand, touched her on the chin to make her look up, up, up at him, and said quietly, Ni quorya.
What Elladan said when he stood close behind her, so that when she leaned back to look up at him against the dappling light he seemed to take up all the space in the world, and he whispered, Le no an-uir nin?
Buffy understood enough to know that this was a situation she could not handle. More than anything she wished she had someone to talk to about it, but Arwen was noncommittal and Elrond was out of the question. Everyone else seem to want to keep their distance, study her from afar, giving her no help whatsoever, not that she could understand much of it if they tried. And this wasn't something that could be solved with violence, much as she wanted to sometimes. What did that leave her with? Buffy was alone in a world in which her only two real friends wanted something from her that she wasn't sure if she could give.
And the strain was beginning to tell on Elrohir and Elladan, too, in their relationship as brothers as well as their relationships with her. They stayed apart for longer periods of time, awkward with each other in a way that she could tell they never had been before, each eying the other in a new, harsh light. Since the day they'd been born, they'd been one in all things, their intentions, their thoughts, their feelings in total agreement. They followed the pattern even now, both wanting, thinking, and feeling things that were both completely the same and absolutely irreconcilable.
So instead she stayed suspended in a kind of hopeless dread, afraid to acknowledge what was happening and afraid to not. When Elladan stood at her closed door in the early night and sang a slow song of courtship, she lay wide-eyed in her bed and said nothing. When Elrohir pressed her back into the sheltering branches of a tree, holding his cloak over her to keep off the rain, and, leaning down, down, down, kissed her softly in the protective circle of his arm, she held back, shied away, and said nothing.
When Elrohir and Elladan, meeting each other on the way, stopped abruptly and silently, detachedly looked at each other over Buffy's head where she was sitting, her heart sank and she said nothing.
And when Arwen asked her, simply, quietly, without judgment, Ma nat?
Buffy answered, with complete honesty, Ala istan.
gwanno ereb nin leave me alone
daro i stop that
ava vanta i salquesse keep off the grass
avo acheno don't look back
ni quorya I am drowning
le no an-uir nin will you be mine forever
ma nat which one
ala istan I don't know