I still have some questions about my translation. Because I doubt that I understood it right.
Can I say : "She was the lady of the house.(I should not have written mistress).
I know that the correct sentence is :"He saw a pretty woman through the window, standing by the fire-place. But can I say :"He saw a pretty woman, standing by the fire-place through the window."
I agree with the previous poster that "Through the window, he saw a pretty woman standing by the fireplace". This makes everyone's location clear.