When Brienne teams up with Podrick (and one or two other characters who never made it into the show) to go looking for the missing Stark girls, they come afoul of Rorge and Biter (locked inside the same cage with Jaqen H'Ghar in the show).
After being released earlier in the story by Arya, Rorge and Biter attack Brienne and Pod at an inn. Biter gets the upper hand and proceeds to eat Brienne's face.
Biter's mouth tore free, full of blood and flesh. He spat, grinned, and sank his pointed teeth into her flesh again. This time he chewed and swallowed. He is eating me, she realized, but she had no strength left to fight him any longer.
Brienne is saved by Gendry (who is still running around the Riverlands at this point in the novels), but she's left with half a chewed-up face.