Katie was Ruby's Spheal/Walrein in the original Nuzlocke comic, Ruby: Hard Mode.
Katie's capture was never shown in the comic. The only reason Ruby pulled Katie, who was a Spheal at the time, out of the PC box in the first place is so that he could teach her Rock Smash and Dive, which essentially made her the team HM Slave. She realized this, and began crying, where she was comforted by Loudred. After Loudred's death, however, she became a permanent member of the team. Her evolutions were never shown in the comic, but she appears in Episode 13 as a Walrein. She helped defeat Drake, however, Ruby's lack of confidence in Katie was the main reason Mr. Humpy died. Sceptile blamed the death on Katie.
Katie died in the final battle against Steven, where she was the second-last Pokemon Ruby had. She was one-hit killed by Earthquake, and Ruby lost the challenge.