"Are you okay? You're looking at me with that look you used to always get just before you'd start kissing me all over and then making out with me, trying to get me in the mood. I hope you're not thinking of masturbating!"
You blush, that did seem like a good option for relief... until now...
But you shake your head, and say that no you won't consider masturbation. You tell her it's against your upbringing and religion.
"That's good, because I'd hate to tell my parents or your parents that you were masturbating! Think how embarrassing that would be if you did it in front of me!" She giggles again.