I like the future world that this story takes pace in, not something that is possible today, but maybe less than fifty years from today. I agree with Feline that it was a challenge to keep track of the personalities at first, but I can't think of a better way to tell this story than you have.
Imagine the challenge for the characters, keeping their own minds with all this going on around them? I would also love to see Amy conspire with the house computer, or even Casandra's husband, to teach a lesson and leave Cassy in maid/concubine mode for a period of time, just to get the full experience. She has her new bar code, and a troublesome maid could always be lent out to the neighbors, or even sold off or re-contracted at the slave market. Does the husband travel at all, to earn his implied wealth? Might he take Amy with him instead, or might the two ladies, being left alone, get into some serious mischief? How similar do the two ladies actually look, or could be made to look, in this future world?
I could obviously see a few more chapters in this wonderful tale; you've taken the time to build the characters and the setting, and I think it would be a shame to leave it here.
In any event, thank you for sharing, Jackie.