In the A Song of Ice and Fire novels, Fat Walda is the second of three daughters of Merrett Frey and Mariya Darry. Merrett is himself the ninth son of Lord Walder. She is known for her gluttony, hence her nickname, which her father considers shameful, though less shameful than her older sister Amerei, known as "Gatehouse Ami" for her blatant promiscuity.
Lord Walder taunted Merrett that Walda is "a sow in silk", her weight being the only reason Roose married her. He remarks that the Freys would have had the same alliance at half the price if "the little porkling" put down her spoon from time to time.
She is described as a round pink butterball of a girl, with watery eyes, a huge bosom and limp yellow hair. Her voice is thin and squeaky. She is fifteen years old when she marries Roose. Walda has a giggling, fun-loving, even charming personality, and is known for cracking bawdy jokes. It is loosely implied, however, that this is simply an outward persona that she affects to fool others into thinking she is harmless, when she is secretly very intelligent - some of her bawdy jokes can actually be quite witty.
[…]
Walda is fully aware that Roose chose to marry her instead of another Frey girl - such as Fair Walda, granddaughter of Stevron Frey - simply so he could get her weight in silver, but nonetheless she is very grateful to him, as marrying the head of a powerful House drastically elevated her social standing. Roose initially thought Walda would be an annoying distraction, but later says that despite himself he has become oddly fond of her. His first two wives were silent and still when he had sex with them, but Walda makes a lot of noise and openly enjoys it, which Roose finds somewhat endearing.
Eli isotissinen sekä todella kiimainen ja himokas semmonen vähän muhkumpi tyttönen… huhhelis huh että muuten kelpais ja maistus……. tosin vähän matalampi ääni olis kyl sexympi kunhan ei ole sellanen miehen kuuloinen.