I read Sarah's comments and her justification with amusement. She seems to belong to that ilk who thinks that she can only have fulfilling sex with the so-called Mr. Right.
The question that remains unanswered of course, is how will she identify Mr. Right? How will she know that Mr. Right is the right sexual partner for her without having sex with him? Will she know because he sweeps her off her feet with roses and diamonds till she falls deeply in love like she romantic she professes to be? And then either marry him first to have sex or have sex with him anyway?
What happens if he turns out to be impotent or inadequate in bed? Will he still be Mr. Right for Sarah? Is sexual pleasure subservient to marriage or to love?
I agree that humans do not having mating seasons, but tyhe purpose of sex is not just mating. It is also pleasure that that's what sets humans apart from most others. Sarah is right. She's naive, but not in the way she thinks. There is nothing wrong in her stand of not wanting casual sex. In fact it is laudable. But her justifications are all over the place.
She seems to think that sex for pleasure is wrong, and there I agree - it is a puritanical concept.