Was she a slave? When travelling in Vietnam (and probably plenty of other places) its pretty common to find the staff at little hotels all sleeping on mats on the floor in the kitchen. Its not a big deal - to get to the fridge you might need to step over and around them. None of these people are slaves, though they are certainly lowly paid workers.

Is it unusual to have this arrangement in a private home? I don't know.

The opprobrium from other commenters seems a little steeped in our own western views as to what's right and wrong, and I think your plan of digging more into the situation sounds an appropriate one.