She hated him. Arya couldn't understand why her sister claimed to love him. He never spoke courteously to either of them. Sometimes, Arya would ask where they were going and the Hound told her not to talk back. When Sansa would get bored and sing, he never told her how well she did like lords and knights were supposed to. He was gross, spitting and making water in front of them. Sansa said it was because Arya had tried to run so Clegane didn't trust her, but she knew better. He was rough. Every morning he would dump Arya into the saddle of his horse and at night he would all but throw her off before grabbing Sansa to mount or dismount. At night, he rolled her in his horse blanket and tied her top and bottom so she couldn't move. And she hated how he looked at her sister, like a hungry dog eyeing a bone.
At night, after Arya was bundled, her sister would sit with her, fingers threading through her hair. It usually hurt because there were so many tangles, but it reminded her of their mother and it was soothing, so she didn't complain. The worst was when Sansa would try to lull her to sleep with stories or lullabies. She didn't tell the good stories like Old Nan did, about the grumkins and snarks Arya and Bran both liked. Instead, she told stories about knights and maids and valor while the Hound sat against a tree snorting and making sarcastic comments. Somehow, Sansa was able to not get upset about her stories being mocked. Wanting them to stop, Arya would close her eyes and steady her breathing, pretending to sleep. At that point Sansa would leave her and Arya hated that the most. It meant she was going to him, to sleep with Clegane.
No matter what Sansa said, Arya would never let the Hound join their wolf pack.
So she would wait… then scream. For Sansa's sake, she would pretend she had a nightmare, usually about their father's death. Her older sister would immediately come running and hold her, speaking soothingly until she or Arya fell asleep for true. In the morning, Sansa was usually awake before her, ready with their meager breakfast. Nothing was said of her nightly terrors, much to Arya's relief. She usually couldn't remember what she had said the night before.
During the days, Sansa started to sing less and less, though. Dark rings began to grow under her eyes and when they would stop to rest, it seemed as if it was harder for her to climb back into her saddle. At one point, Clegane even had to tie Sansa's horse to his own saddle because she couldn't control the docile mare any more. And the Hound grew surlier each day. Once, when Arya asked nicely for a song, he cursed at her and told her to shut it. That night he really did dump her from the horse.
After getting bundled, Sansa sat with her like before, but her voice had grown soft and weak. With the Hound sitting quietly, Arya found herself starting to doze off. She didn't hear or feel her sister step away, but woke with a jolt when she realized the other was gone.
With a slight twist of her neck, she found them sitting under a tree. Their cloaks were wrapped tightly around them, so she could only see their faces, but she hated even that. Sansa was facing the Hound, her mouth open and face scrunched up as if she was in pain. Her breaths were short, labored as if she was trying not to scream or cry out. But the Hound's face was worse. The unburned side was relaxed, his usual scowl gone. Instead, he was watching her. His face was like… Arya tried to place it. Like Septa Mordane when she talked about the Seven. Like her father as he sat before the heart tree in Winterfell's godswood. She hated his stupid face for that. Sansa wasn't a weirwood, she was her stupid sister. He had no reason to look at her like that!
Suddenly, Sansa's hand flew to her mouth and she bit her knuckles. Hard from what Arya could see. After another moment, Clegane brought his own hand to his face and he sucked two of his fingers. And Arya hated him for looking like he enjoyed what he tasted. Having seen enough, she screwed her eyes up tight, took a deep breath, and screamed and thrashed in her bindings. She did her best to hide her satisfaction when Sansa gave a surprised "oh!" and the Hound cursed.
When she felt her sister's hand, Arya slipped into the lie easily. "Oh, Sansa," she whimpered. "I had a nightmare, it was horrible! I saw father-"
"Shut it," Clegane snarled from her other side. He roughly turned her to face him. "Stop lying, wolf girl. She's not your mother, your nurse, or your septa. Grow up! You don't need her every second of the day. Let her sleep! And you," this time he pointed at Sansa. "Get some sleep. You're half dead! No more running between us. At night, we make camp, you pick one and stay."
Sansa weakly agreed before the Hound rose and stomped away. She draped her cloak over both of them and instantly fell asleep. For a moment, Arya felt bad for keeping her sister awake every night. But it wasn't her fault Sansa kept wandering off to sleep with the Hound. If they just stayed together, everything would be fine. Convinced she was right to save her sister from the monster, Arya fell asleep herself.
In the morning, she was pulled roughly from Sansa's embrace and untied. Clegane gestured for her to keep quiet before giving her a chunk of sausage for breakfast. As she worked at it, Arya watched as he knelt by her sister and gently shook her shoulder. Sansa seemed to wake in stages, first trying to burrow into her cloak before softly opening her eyes and turning to him. He said something too low to hear, but her sister nodded and slowly rose to her feet. A pang of regret hit her as Sansa seemed to wobble and Clegane had to hold her steady.
After finishing their breakfast, the three rode in silence. Reaching a river swollen from rain, the Hound growled at Arya to be quiet when she asked if it was the Blackwater Rush. Sansa said nothing. That night, her sister only kissed Arya on the cheek before curling up next to the Hound, and each night after she alternated who she slept with.
And Arya hated it.