She was the daughter of an old wisewoman who was a healer, and also practiced healing herself. Her greatest treasure was a bolt of scarlet silk from Asshai, which her grandmother had taken from the wreck of a cog that had washed up on the Frozen Shore. She was very generous.
During the time when Mance Rayder was still a member of the Night's Watch, he was on a ranging beyond the Wall when he was attacked by a shadowcat. The shadowcat's claws shredded his cloak, arm, and back, and his other brothers of the Night's Watch were afraid he would die before he could be brought to Maester Mullin at the Shadow Tower. They brought him to a wildling village where they knew an old wisewoman lived, and though she had passed away, her daughter took care of Mance. She cleaned his wounds and sewed them up, and fed him porridge and potions until he had recovered. While he recuperated, she mended his torn cloak with swatches of her treasured red silk, as a gift to him.
Upon his return to the Shadow Tower, Mance was given a new black wool cloak to replace his mended one. Ser Denys Mallister, his commander, admonished him that the Night's Watch only wore black, and that the red-patched cloak was not uniform, now only suitable for burning. Because of this infringement of his freedoms, Mance deserted the Night's Watch to live with the free folk in the way he wished.
A Storm of Swords
Beyond the Wall, Jon Snow encounters Mance Rayder, who still wears the patched cloak, its red silk now faded. Mance tells him the story of the shadowcat, the wisewoman's daughter, and the silk-patched cloak, and how that led him to desert the Night's Watch.
A Dance with Dragons
At the Wall, the captive Mance Rayder is apparently executed by King Stannis Baratheon, burned by his priestess Melisandre. When Mance is led to the place of execution, Jon Snow notes that he is only wearing a thin tunic, that they had taken away the cloak the wisewoman's daughter had patched with red silk.
At the Shadow Tower, I was given a new wool cloak from stores, black and black, and trimmed with black, to go with my black breeches and black boots, my black doublet and black mail. The new cloak had no frays nor rips nor tears... and most of all, no red. The men of the Night's Watch dressed in black, Ser Denys Mallister reminded me sternly, as if I had forgotten. My old cloak was fit for burning now, he said. I left the next morning... for a place where a kiss was not a crime, and a man could wear any cloak he chose.