You have altered the deal

If Sara wants your cooperation, it'll have to go both ways. Not to mention the fact that you're sick of her scowl. "Listen up Mother Superior, I've realize that you've been treating me rather poorly." She scowls deeper than ever. "What?! You say that even as I let you-" You interrupt. "Ah ah, there it is again! SO rude. If you want me to uphold my end of the deal, you need to be a little more civil" you say, still pounding into her. She bares her teeth at you silently. "If you want my cooperation, I'm going to need you to give me a nice smile" you say, with an evil grin of your own.

"You little bastard!" she yells, "I'll do no such thing! You're lucky I've not thrown you out int the cold, let alone this!" You feel yourself nearing orgasm as she squanders her chances. "Ah yes, this. It would be a shame if the nuns found out, wouldn't it? Not that I'm threatening. More just pointing out that you don't hold the cards here. Make your choice Sara, just give me one, simple little smile or don't." Sara's face looks like a guard dog about to bite an intruder. "You little piece of shit, so help me-" So, she has made her choice.

You drop down from the backboard, laying yourself on top of Sara's motherly body, enjoying it while you can. She's soft like a pillow, and her breasts feel so sweet as they press up against your hard body. You wrap your arms around her head so she can't wiggle free. You feel her start to claw at your back, but it is entirely ineffectual at anything but maybe leaving a red mark. You thrust powerfully between her spread legs despite her struggles, balls heavy with seed slapping against her. You can feel that you're almost there, and with one final thrust you bury yourself up to the hilt. You moan loudly as you blast her neglected pussy with your hot young essence. Despite herself, you can feel her quiver with enjoyment as your warmth fills her. Panting, you break your headlock and get up. "There's that smile"