Who is Lucile Angellier from Suite Franaise and what is their importance?

Lucile Angellier is described as beautiful, quiet, withdrawn, and sad. She appears to have given up on her life, and she lives imprisoned with a bitter mother-in-law, whose only focus is the misfortunes of her son. Lucile and her mother-in-law do not like one another at all, so Lucile, childless, is mostly alone in a very large, opulent chateau. Lucile is married to Gaston, whom she does not love and whom she knows loves someone else, and up until a German officer is billeted in her home, she is depressed and desperate.