What was the life of a slave like in Mexico City in the late nineteenth century?

I’m extrapolating from the story of Siki which I found in this book

She was captured in 1870’s by the Mexican army, taken to Mexico City, sold as a slave to work on a hacienda. I am wondering what her life would have been like. Was she treated as a domestic, field hand, or concubine? Was she indoctrinated into Christianity? Did she learn Spanish? Where did she sleep? How many others like her were there in that place?

I’m not asking to know specifically about her (although that would be delightful!) but about people like her. And I’m not asking for idle speculation either, as speculating I have covered. But if anyone has a sliver of knowledge on the subject, I would be most appreciative.