Discourage her.

You need to get a grip on this before it all spirals out of control. You live in a fairly small town. News travels fast, and nothing remains a secret for long. Your entire life might come crashing down all because of one crazy-horny girl who has her eye on you. You delete the photo, along with the rest of the nudes saved to your phone, and send her a message.

You have to stop this. I love my wife. I barely know you. You're young enough to be my daughter.

Her response is swift, and you detect, somewhat defensive.

You weren't saying that when you were cumming down my throat three times.

You decide to soften your tone slightly, in case you hurt her feelings too much.

Look, you're an amazing girl. But there are plenty of great guys your own age out there. I'm just not one of them.

You finish your dinner as you await her reply. You hear nothing until after you've finished cleaning the dishes, and your phone buzzes almost angrily with her curt response.

Fine.

You exhale deeply, hoping that this is the end of the matter, and head upstairs to settle for the evening.