Your Shapeshifting girlfriend turns into Your Bitchy Little Sister

...my little sister.” You say rather sheepishly. “Oh, got the hots for the cheerleader, huh?” Your girlfriend states with a wink as she clambers on top of your dick. As you begin thrusting her moans become higher in pitch, her eyes turned to a beautiful light blue, and her hips widen pressing her now beautiful, heart shaped rear into your groin. Her stomach tightens into a firm six pack and her nipples enlarge and breasts swell out to a hefty D-cup while her limbs grew slimmer. As your girlfriends face begins to pop and change shape, her curly brown hair becomes straight as a ruler and brightens into a blonde while growing down to her waist and tying itself into a high ponytail. Your girlfriends formerly dainty round face has formed into your teenaged bratty sister's face. Finally, her fingers grew longer and daintier as black nail polish applied itself to her long fingernails and toenails. Now your sister's identical twin, she comments in her bitchy voice while rolling her eyes, ”God, is this going to take much longer? I'm, like, totally going to be late for practice.” Upon which you release your semen. “Okay that was, like, super hot. Thanks again for helping me get off before practice, big bro.” Your girlfriend/sister says as she cuddles up next to you. Picking up her role playing queue, “Anytime, sis.” Grabbing her by the ass and pulling her in for a kiss. “So what now?” She says, placing her manicured hand on your chest.