I think "SP" means a woman who is offering a service to the public.
Women who use sex to get ahead at the workplace very rarely engage in a direct quid-pro-quo. "I'll give you a BJ for a raise" just doesn't really happen.
What happens is that junior women in an organization form relationships with men in powerful positions--which is what women do everywhere. It's not even necessarily calculated--she probably really is attracted to the guy, because women are naturally attracted to guys with power and status. In any case some sort of relationship is formed--it might just be a flirty friendship, it might develop into a full blown affair. Sex isn't being explicitly traded for opportunity, instead, it's used to build up a relationship with key people. A form of networking. Some people form networks by playing golf, attractive women form networks by flirting, sometimes having affairs. But they are networks--the result is they become friends, no deal is made.
What happens next is that over the years as the woman moves through her career the guy will help out his friend now and then--referring her to a position he knows is open, putting in a good word for her with the hiring manager, giving her a bit of advice that other people don't have on how to approach an opportunity. Once you have a relationship with someone powerful, the benefits are ill defined but real.
That sort of thing gets really blurry and calling that woman a prostitute, I think, fails to hit the mark.