0 the wife of a marquess (= a man of high social rank), or a woman who holds a high social rank in her own right --
This may have been at least partly in order to end problems connected to the inheritance of the estate following the death of the marchioness' first husband.
From "marquise", which means not only a marchioness but also an awning.
In the background, green trees can be seen, which are not very detailed and contrast with the white dress of the marchioness.
The book in question had particular relevance for the marchioness at that stage of her career.
