"Replacement Value" by Parker.
http://www.dejanews.com/getdoc.xp?AN=196945883 (*)

While her fiance is off in Mexico City undergoing some sort of training for a NAFTA-related job, the American woman is living in Mexico, where she befriends a woman with expensive tastes.

Because I am such a sophisticated reader, it was almost at once obvious to me that Sandra was subtly being recruited by Terry to become one of the whores in Pedro's stable, but I could not immediately figure out what impact this would have on her relationship with her fiance or why the story was entitled "Replacement Value." So I had to read the rest of the story - as you should.

I find Parker to be an extremely good writer who gets bizarre ideas, which he tries to incorporate into clever plots. Sometimes he succeeds; but sometimes he simply fails to convey to me how his plots make sense - the emotions sometimes just don't sound plausible. This is one of the good ones. Everything falls perfectly into place at the end. It's not a pleasant story, but it certainly is creative and sexy.