Talk dirty to her.

You give up on the direct approach, and try to get her horny. "You know, you are so beautiful. I'm just aching for you right now. You make me so horny!" You casually point to the guy that briefly saw her tits earlier. "I'd even bet you're making that guy over there hot and hard."

She swung her hair around, and quickly glanced at the blonde haired stud, staring at her. Her face flushed beet red, before returning back to you; but not before greeting him with an encouraging smile.

You could only ogle yourself, at the sudden swell caused by the nervous heaving in her breasts. "Just the thought, that he wants to suck on your tits, makes me hard. And, judging by the way you're acting, I'd bet you're thinking along the same lines."

She has since returned to her lying position, determined to get the tan on her back. She dug her toes into the sand and uttered a soft moan.

"C'mon, think about him ogling at your body. Imagine him jerking off, thinking about how beautiful you are. Think about what would be going through his mind; about what he'd like to do with you." You watched as your girlfriend wriggled her hips, making her bed a little more comfortable.