She knew Quinari didn't have sex for love.
They were simple. They showed that they loved each other through their actions and had sex for fun. The first time she and Bull had sex was a month after he had joined the inquisition, working for her, and she still couldn't walk a week later.
When he didn't approach her again she felt somewhat hurt until she remembered that sex honestly didn't mean anything other than fun. It was a week later when he gifted her a new holster for her dagger. In return, a month later, she gifted him with a new eye patch. It allowed him to sense anyone standing in his blind spot. They had sex again two weeks after that.
She made the next move out of turn and insisted he come with her to investigate about the dragon in the Hinterlands. That didn't go over too well when the damn thing had kicked her before snatching her out of the air and flinging her off of a cliff. The others had to come to her rescue and immediately returned to Haven. Still yet he showed his appreciation by ignoring everyone else and started training with her the moment she asked him to. She'd never healed so quickly. When she was back in perfect health they did more than have sex.
He had proven his interest and she had reciprocated. This time he presented her with a collar. It would be secured around her neck and only he would be able to remove it. While she wore it he would be in charge. She would follow his orders without question. She would submit to him. He had promised her at the beginning of all of this that he would never hurt her and she need only speak one word and everything would end. In the months that followed she never even considered speaking it.
Then one day he came to her fuming, shoved her collar at her and impatiently hurried her to get ready for him. She knew he was keeping in mind, somewhere all the way in the back, that he had to be careful not to hurt her. That didn't seem to be enough today as he went further than they ever had. He was brutal and unyielding. She told herself repeatedly that she would brave through it, he clearly needed this tonight. It wasn't until near the end that she second guessed her decision. He gripped her neck and squeezed so tightly she lost consciousness.
The next morning she woke and couldn't stop herself from crying. He had apparently collapsed on her and she was already in an excruciating amount of pain. She couldn't breathe. She couldn't whimper, she couldn't make a sound. She couldn't move, he was crushing her. Panicked, her magic exploded from within her and tossed him across the room. She slowly curled up on her side and as she gasped. Then she heard him, then she looked. He looked terrified as he slowly approached her, his arms out stretched towards her. She was finally able to make a pitiful whimpering sound as he reached for him. He rushed to her and scooped her up.
She was completely naked so he wrapped her in the sheets and rushed her to Dorian. The man hurried them into his rooms then sent bull to fetch Solas. She only wanted everyone to stop moving her. Every movement felt like it was killing her. She just wanted Bull to hold her as she slept. Sleep she did but solas invaded her dreams as well as her waking hours alongside Dorian. Bull though, he disappeared day one and did not return. After a few days of sleep, potions and healing magic she was finally told what had gone on. Bull had done her so much damage that she looked half dead. She'd had a broken rib, her pelvis bone was fractured and you couldn't even see her properly under all of the bruises and swelling.
She spent another week healing before they let her out of bed.
She immediately went to the Chargers and had them bring Bull to her. A coward he was not and so he came to her to be rejected face to face over what he had done. When she handed him the collar he certainly looked like he could be blown away by a weak breeze. When she next turned her back and moved her hair aside he froze. She couldn't have possibly been offering him another chance. He deserved worse than death for what he'd done. Internally she was trembling, she wouldn't be able to hold it together if he rejected her.
The Chargers stood around them, witnesses to what she was giving back to their leader. They all looked at him expectantly. When he looked ready to turn and run they grew worried, but they need not have been. He finally stepped forward and secured the collar around her neck and lowered them both to the floor as he held her. He listened to his Chargers as they left him and silently thanked them in his mind for being his strength in that crucial moment.
No one second guessed the couples decisions as they watched the two heal each other in only the way that they could. They had come back from something that could have broken them and were stronger for it.