Demand she pleasure herself while you watch.
From Create Your Own Story
"I want you to reach back between your legs and play with yourself," you say quietly.
"What?" She asks.
"You heard me," you reply, waving the gun at her a little.
She sighs angrily, then does as she's told, pushing her hand between her legs and using three fingers to rub at the lips of her quim. There's very little sexy about it. It's not like she's doing it because she wants to, she's simply going through the motions.
"You better make yourself wet," you warn her. "Because I'm about to come over there and fuck you."
She sighs angrily again, then slows her fingers down, using the index and ring finger to spread herself open just a little, and her middle finger's tip to dip just barely into the pink. Slowly, she pushes the pad of her finger against her tight opening, then rolls it in a little circle, moving her hips ever so slightly as she does so. Then she slides the middle finger down, between her lips and onto her clit, rolling it in little circles. Her round ass shakes just a bit as her hips gyrate, and your cock is so hard, you can barely take another second of it.