From A Wiki of Ice and Fire
|Book(s)|| A Game of Thrones (Appears)|
A Clash of Kings (Appears)
A Storm of Swords (Mentioned)
A Feast for Crows (Mentioned)
A Dance with Dragons (Mentioned)
She has curly auburn hair.
A Game of Thrones
Beth is present during the session of needlework with Princess Myrcella Baratheon at Winterfell. There she overhears the discussion between Sansa Stark, Jeyne Poole and Arya Stark about Prince Joffrey Baratheon.
A Clash of Kings
During the closing banquet of the harvest feast, Beth is seated at the main table beside her father, Ser Rodrik Cassel. After the dinner, she is invited to dance by Lord Wyman Manderly and Cley Cerwyn.
Beth is one of the prisoners at Winterfell when the castle is taken by Theon Greyjoy. Theon used her as a hostage when her father tries to take the fortress back. After Ramsay Snow's treason and Winterfell's sack by the men of House Bolton, she is taken to the Dreadfort.