I comfort myself with the knowledge that I based my book on the facts Jane Austen supplied herself, in Darcy's letter to Elizabeth, so I am not writing anything she did not herself suggest. But that is not entirely true, as I did invent a few things along the way that she probably did not contemplate, though they do not contradict anything she wrote.
A happier excuse is the fact that Jane Austen herself liked to think of her characters as extending outside the four corners of their written story. The fact that she put so much thought into their relationships, their names, who they were named after, etc. even though these details are not essential to the story, is evidence of this. But better evidence is her letters.
In one letter in particular she talks about a pass-time of hers, which was to go to portrait galleries and try to find paintings of her characters among the faces. She writes in one letter to her sister, Cassandra,
"I was very well pleased, particularly (pray tell Fanny) with a small portrait of Mrs. Bingley, excessively like her.
I went in hopes of seeing one of her sister, but there was no Mrs. Darcy. Perhaps, however, I may find her in the great exhibition, which we shall go to if we have time. I have no chance of her in the collection of Sir Joshua Reynolds's paintings, which is now showing in Pall Mall, and which we are also to visit.
Mrs. Bingley's is exactly herself -- size, shaped face, features, and sweetness; there never was a greater likeness. She is dressed in a white gown, with green ornaments, which convinces me of what I had always supposed, that green was a favourite colour with her. I dare say Mrs. D. will be in yellow."
This actually makes me wonder why Jane is not always depicted in green in adaptations of Pride and Prejudice, and why we do not more often see Elizabeth in Yellow.
If I ever stage or film my own adaptation, I shall be sure to apply these preferences.
Follies Past is a prequel to Pride and Prejudice