Louisa Parker first appears in Sharpe's Rifles. She was the niece of Methodist missionaries in Spain and was described as bright eyed, dark haired, with mischievous smile. She was quietly courted by Don Blas Vivar, and by novel's end, she had agreed to marry him.

She and the count eventually had five children, two of whom died in infancy (Sharpe's Devil).

She reappears in Sharpe's Devil, which takes place some  dozen years later, traveling to Sharpe's farm in Normandy to ask his help in discovering the fate of her husband and his old friend, Don Blas. She provides him with 2,000 guineas traveling money for bribes and expenses, and also arranges with Lucille for repairs to the farm, and a generous fee for Sharpe's services.

Sharpe is, of course, successful, and returns her husband to her.