Touch
She'd never been much of a touchy-feely sort of person. Having people touch her reminded her of things she'd rather forget ... of touches that hurt, from people who weren't supposed to hurt her.
So she'd retreated, using her mouth as a shield. Practiced sarcasm as a sword to hurt others first so they couldn't hurt her. Obnoxiousness to draw people away from the idea that she might be soft and pliable under the hard, angled exterior.
Only one person dared touch her, and he did it all the time. His hand, whenever he was within reach, found a way to brush against her arm, tickle her fingers or sit on her lower back, urging her forward ahead of him. His eyes caressed her with every glance, making her tingle from top to bottom and break out in a sweaty flush. His breath, when she was close enough to feel it on her skin, flipped the master switch to her nervous system and caused her to light up with desire.
It scared her. His touch was the one uncontrollable thing in her life. She liked having control. Most people would argue that she was always out of control but that was because they didn't understand that she lived in a state of controlled chaos. She chose when to fly by the seat of her pants. She chose when to find a man and use him to satisfy her desires. She chose when to obey the rules and when not to.
His touch threw her into complete chaos, unable to control herself but unable to say no. It was the one thing she wished she didn't love so much.
But the one thing she couldn't live without.