"Boone would ask her how her hair got so dirty and she'd just smile." (Shannon-centric.)
Sawyer wants to fuck her.
She has always been able to tell that sort of thing. She told Boone that one afternoon, when they were eating, and he'd nearly spit out his boar ribs (or thighs or wings or whatever they were). He'd looked at her in disgust, but hadn't said anything.
Shannon finds it incessantly amusing that her high and mighty, pseudo-vegetarian brother is now forced into chewing on pig meat for sustenance.
But, anyway - it isn't just Sawyer.
Everyone wants a piece of Shannon.
To Sawyer she would probably be a conquest. He would be rough, and they wouldn't even undress. He'd push her up against a tree, lift her skirt, drop his pants, and fuck her. Maybe even within earshot of the camp. She couldn't decide whether he'd kiss her or not, but if he did, it would be long and deep, with lots of tongue. His stubble would scratch against her neck and cheek and make her forget about the bark digging into her back. She would bite his lip when he came, /hard/.
When they finished he'd zip his pants back up and smirk at her, maybe call her a name. He'd leave but she would stay, leaning against the tree, breathing so hard she'd be on the verge of another attack. Eventually she would calm down and return to camp. Boone would ask her how her hair got so dirty and she'd just smile. And then he'd know, but the scratches on the backs of her thighs would still be her little secret.
That was just with Sawyer, though.
It would be different with Sun. To Sun she would be a forbidden object - the Pandora's box of Shithole Island. They would go somewhere far away, on the beach or in the grass (preferably in the grass, because Shannon hated the feel of sand on her skin).
With Sun it would be less like fucking and more like something else. Her skin would feel smooth and clean and cool. Everything would be silent, save for their short gasps and moans; they didn't even speak the same language, after all. The sex would be light and pleasant, but also sad. They would share little smiles around the campfire at night but no one would really notice, and Shannon could just tell everyone that Sun was helping her with breathing exercises when they had to disappear. It would almost be true.
For Hurley she could be a fantasy: the hot, skinny cheerleader who'd never look twice at him back in civilization. She'd pretend to be a coked-out groupie for Charlie, stroking his chest with her fingernails and his ego with her sugared voice, screaming his name when she came. (She would be on top.)
Claire would use her for validation, to assure herself that she was still desirable despite the giant belly and red-rimmed eyes. Kate would find solace in Shannon, and whisper secrets in her ear while her fingers teased. Jack would feel guilty and convince himself afterwards that he had genuine feelings for her. He would confess his indiscretion to someone, possibly Kate, and an awkward triangle would form between the three of them until Shannon was bored with it and moved on.
Sex with Michael would be the most traditionally enjoyable - he'd take his time and probably go down on her. He wouldn't even think about his son. Sayid, though, would fight his attraction all the way to the end. Her long legs folding around him would make him shudder, and he'd feel shame that it was in a good way. Later her brother would wonder to himself why Sayid never looked him in the eye anymore.
Jin was the only one who wouldn't sleep with her - unless he saw his wife and someone else together and decided it was time for a revenge fuck. Even then it would be all about Sun, and life would go on as usual the next day.
For now, though, there is Sawyer. He's reaching the end of his rope. (She's always been able to tell that sort of thing, too.)
He'll keep her entertained. For a little while, at least.