You make her like it, and she cums.

Jenna rides your hard, thick cock up her pussy. Your hot young girlfriend bounces up and down in your lap, taking your shaft deep, her soft little tits rubbing in your face. Jenna holds onto your shoulders, you hold onto her tight, tiny little ass, and she moans as she rides you. "Oooh, yes! Yes! Yes!"
Little Jessie watches the two of you fuck, loving every second of it, every thrust, wishing that was her on your cock.
Then Jenna throws her head back, arching her back. You feel her pussy constrict around your cock, flooding with her wet, juicy orgasm. She moans and writhes and bucks, cumming hard. It's so good, you cum too, hard, bursting inside her, filling her hot sweet pussy with your seed. Jenna kisses you, sweaty, panting, and slowly slides off you. Jessie looks so turned on, staring at her sister's pussy dripping with your cum.

(Mark +1 xp for making her cum)