Visualizing you sucking her penis turns her on

You're not quite sure what Sam has in mind, but you're always trying to gently nudge her out of her inhibitions, so now's not the time to question her.

You open your mouth and start to lean forward. But before you can stick your tongue into the folds of her jeans between the teeth of her zipper, she pushes her closed fist down between you and your target. With the heel of her fist against her crotch, she sticks her thumb up and out, so that it points at your face at the same angle an erect penis would have, were Sam a man, and not a woman!

You pause, uncertain what to do.

"Suck!"

You look up in response, but she puts her free hand down on the back of your head and shoves your face closer to her erect thumb. "Come on, Paul, you said you'd give me a blow job if I wanted you to. Well..." Unable to fully contain herself, she giggles. Then she regains her serious demeanor. "Well, I want you to suck my dick. Now!"