In order to fund her struggling attempts to be a writer, Dana works at a temporary agency, doing various jobs for minimum wage. Interestingly, in chapter 3 she makes this statement:

I was working out of a casual labor agency—we regulars called it a slave market.

Dana's casual reference to a slave market doesn't exactly capture that situation. She is being paid for her work, can leave when she wants, and is allowed the freedom to pursue the work of her dreams through this job.

Of course, the term becomes a bit more meaningful and personal when Dana is transported back in time to the Weylin Plantation. She is forced to please the wife of her master, who hates Dana, in order to avoid beatings. She attempts an escape and she faces a beating for that. She watches Alice be forced to submit to the sexual desires of Rufus and to then have his children. Dana eventually reads of a slave market which hits much closer to home than the one she casually joked about earlier:

And in later papers, notice of the sale of the slaves from Mr. Rufus Weylin's estate. These slaves were listed by their first names with their approximate ages and their skills given.

Because Dana kills Rufus, his slaves are all sold off, and Dana understands that these faces she grew to know as true humans, with stories and sufferings all their own, truly faced the slave market of this historical era. Dana knows that because of her they likely faced even more difficulties in being sold again. She has thus indirectly influenced the slave market involving many of her former acquaintances and friends.