Eliza Williams is a character mentioned in Sense and Sensibility. She never appears in the book.
She is the ward of Colonel Brandon, though many people (Mrs. Jennings included) believe her to be his illegitimate child. She is truthfully the daughter of his cousin, childhood sweetheart, and former sister-in-law, also named Eliza, and Eliza the Elder's unnamed lover. Her mother died when Eliza was three, and Eliza the Younger became Brandon's ward.
For several years Eliza lived at school where Brandon visited her often. She visited him at Delaford following the death of his brother and his inheritance of the estate.
When she was fourteen, Brandon withdrew her from the school and placed her in a household in Dorsetshire run by a respectable woman, with several other girls her age. She lived there for two years.
When she was sixteen, Brandon gave his consent to her visiting a friend in Bath where the friend's father was convalescing. The two girls ran wild while the father was confined to the house. It was in Bath that Eliza met John Willoughby, who seduced her, and in February, they disappeared together. Brandon did not hear from Eliza for eight months. Her friend refused to give him any information when he tried to find her, and her friend's father had no information to give.
Eliza lived with Willoughby for several months before he left. He did not tell her his address, and he did not return to her like he had promised.
In October, Eliza writes to Brandon at Delaford, and the letter is forwarded to Barton. Brandon cancels a planned excursion to Whitwell to find Eliza in London. Around this time, Willoughby's aunt Mrs. Smith finds out about the affair and insists Willoughby marry Eliza, but he flees Allenham rather than do so.
A fortnight later, Willoughby returns to London, and Brandon challenges him to a duel for Eliza's honor. Both escape unwounded.
Eliza gives birth shortly after reuniting with Brandon, and when she is recovered from the birth, Brandon removes her and her child to the country.