He would cheat on her

In her fantasy, he had been looking at another woman again, and she was into it. He would put his hand on her leg, but then quickly take it off, thinking better of it. She would put her hand on his thigh, before slowly sliding up to his crotch. He'd say that they shouldn't, and she'd give him the chance to back out, but he wouldn't. She'd get on her knees, and take out his cock. It would be bigger than she expected, but she'd suck it anyway. Then, once it was nice and hard, she'd lean back and spread her legs. He'd wait though, and return the favor, rubbing and eating out her pussy first, but making sure not to let her cum, keeping her on edge. Finally, he'd thrust into her, and she'd cum at once. He would keep going, fucking her like the animal she was, until he finally managed to cum.