Eliza Williams is a character mentioned in Sense and Sensibility, she never appears in the book.
She is the ward of Colonel Brandon and was seduced and impregnated by John Willoughby, a flirt and a rake. News of the illegitimate child reaches his patron and aunt Lady Allen, who disinherits him. Willoughby has to marry an heiress, and he chooses Miss Grey, a society debutante with a dowry of £50,000, a fortune.