Who is Lucille Lassan from Sharpe's Christmas and what is their importance?

Lucille Lassan is a French woman from Segligese. Sharpe lives with Lucille without benefit of marriage. The couple has a son named Patrick, who with his mother, is taken and held for ransom by Lorcet and his men. Lucille is described as feisty, and unyielding, although, admittedly frightened.