Eight?! Advanced reader. The subject matter is a bit old for eight, no? My daughters were considerably older than that before they knew what being a “mistress” would imply.
I think I probably did not understand the actual definition of mistress. But, I understood the book. I was an advanced reader. By the time I was 10, my teacher was searching for books that I could read for class. Yes, I did read all of the usual, Nancy Drew, Hardy Boys, Trixie Belden, Little House etc. However, I enjoyed the classics early. Particularly, Poe.