Ask her to prove it.

She looks a little taken aback but leans in to kiss you fiercely, her tongue dancing up a storm in your mouth. Amazed, you fall back onto the bed, and watch with shock as your girlfriend slides her hands into your boxers and lewdly begins jacking you off. Her fingertips move just enough to tickle your dick as she slides her palm up your shaft, and when she reaches the head, she spends a great deal of time around it. She stops for a moment, reaching down to yank your boxers off, then surrounds your dick with her hand.

"How's that feel?" she asks softly, watching her own hand with interest.

"Great," you finally groan, reaching up to grab her tits.

"Good. You still think I can't get you off, baby?" she asks sweetly, jacking your cock harder. You try to say no, but Jess keeps beating your dick, rubbing the balls, the head, and mostly the shaft.

Without warning, you feel the cum rise to the surface. Your balls tighten and send a spurt of jizz onto Jess' upper arm, then a jet lands on her tits. Soon, her hand is covered in white goo, and she laughs as she looks at you.

"God that was fun," she says. "What do we do now?"