What is the story of Eliza and her daughter Miss Williams? How is Willoughby connected?

Colonel Brandon was once in love with a ward to his family, Eliza, who was forced to marry his brother while he was sent into the army; the marriage was not happy, and after their divorce, she became a fallen woman and had an illegitimate daughter. Colonel Brandon finally found her when he came back from India, but she was dying in a poorhouse, with her young daughter. Colonel Brandon placed the daughter, Miss Williams, in care after her mother's death, but she had disappeared some months ago after becoming pregnant by Willoughby and then being abandoned by him. Colonel Brandon received news of Miss Williams's state on the day of the Delaford picnic, and this was the reason he left Barton so suddenly and could not return. The Colonel hopes that knowledge of Willoughby's blackness will help console Marianne about her loss, as she is lucky not to have been married to such a thoughtless