Instead of calling it slavery could the authors(othernovels included) say its something else like "employment agency" or something .They could even invent a new system.
In this case its more of cross between a employment agency and serfhood. Serfs are above slave rightwise.
that's fairly unlikely to happen, tho it does have some fun potential.
personally i would just be happy to see the mind fuck that would happen if they saw her now that she is healed.
i mean she was practically dying by the time he bought her.