I think it's about two people who had sex (or near enough), one of whom is less comfortable with it conceptually and idealizes some other woman. The narrator points out that she's right there, in flesh and bone, no distant pure ideal; and seems to hint that he's up against a choice, and sex with her is an option; she seems to feel he is judgmental of her on the basis of what's passed between them.
I think it's about two people who had sex (or near enough), one of whom is less comfortable with it conceptually and idealizes some other woman. The narrator points out that she's right there, in flesh and bone, no distant pure ideal; and seems to hint that he's up against a choice, and sex with her is an option; she seems to feel he is judgmental of her on the basis of what's passed between them.