Isla can be seen watching the Jonas Brothers perform live in "The Ring" and later be she can be seen sitting with the popular girls' clique in "Insheeption". She appears again seasons later and plays a much more significant role in the Season Twenty-One episode, "Doubling Down", where she and the other girls take Heidi out to dinner to celebrate her break up with Eric Cartman, but later begin to tease her and make her feel guilty. She plays another major role in the following episode, "Moss Piglets", where she is portrayed as one of the victims of Heidi's bullying.
Isla has wavy, shoulder-length dark brown hair with a lock of it hanging down the center of her forehead, identical to Kal's. She wears a red sweater with green pants.
When dressed for bed, Isla wears a red top with white lace trim and red pants.
In the episode, "Doubling Down", Isla imitates Cartman to mock him and his relationship with Heidi and does so near perfectly. This suggests that like the other girls, Isla may have a personal vendetta against Cartman, and speaks of him rather harshly.
In "Moss Piglets", another, more prominent aspect of Isla's personality is shown. She becomes deathly afraid of Heidi since the latter's transformation, and speaks of her very carefully to avoid conversing with her. She is shown to be timid, perturbed, and silences and submits herself easily to whomever she feels intimidated. Her sudden shift of personality from witty and facetious to delicate and fearful between "Doubling Down" and "Moss Piglets" could be directly influenced by Heidi's mistreatment and imminent joy of targeting her.
- "Marjorine" - Seen with the "popular girls", playing with a cootie catcher.
- "Tonsil Trouble" - Seen in the background on the playground.
- "Super Fun Time"
- "Breast Cancer Show Ever" - Seen watching the fight; background only.
- "Elementary School Musical"
- "The Ring" - Seen watching the Jonas Brothers.
- "Eat, Pray, Queef" - Seen in the school hallway.
- "Fatbeard" - Seen in the school hallway, hearing Cartman's recruitment announcement.
- "Butters' Bottom Bitch" - Seen in the hallways; background only.
- "Insheeption" - Seen sitting with the "popular girls".
- "Coon vs. Coon & Friends" - Seen at the Justin Bieber concert.
- "Funnybot" - Seen from behind in the cafeteria.
- "1%" - Seen at Clyde Frog's funeral.
- "Cartman Finds Love"
- "Let Go, Let Gov" - Seen at the school playground.
- "Gluten Free Ebola"
- "Where My Country Gone?" - Seen on the playground.
- "You're Not Yelping" - Seen in the hallway.
- "Sponsored Content" - Seen in the hallway.
- "Skank Hunt" - Breaks up with Brimmy.
- "The Damned" - Seen in the hallway.
- "Wieners Out" - Seen in the stands at the volleyball game and in the cafeteria.
- "Douche and a Danish" - Seen making danishes in the school cafeteria.
- "Fort Collins" - Seen in a photograph on the wall of Heidi's bedroom.
- "Holiday Special" - Seen in the crowd.
- "Hummels & Heroin" - Seen at Marcus' birthday party.
- "Doubling Down" - Takes Heidi out to eat with the other girls. Teases her for her relationship with Cartman, although playfully, she unintentionally hurts Heidi's feelings when she imitates Cartman.
- "Moss Piglets" - Is verbally attacked by Heidi in the school cafeteria, and at the bus stop.
- "SUPER HARD PCness" - Seen in the hallway evacuating to the gym.
- "Splatty Tomato" - Seen during an argument between Eric and Heidi near the Community Center.
- "A Boy And A Priest" - Seen at Clyde's party.
- "The Problem with a Poo" - Seen in the school assembly.
- "Tegridy Farms" - Seen at the school playground.
- "The Scoots" - Seen at the Dr. Spooky's Pumpkin Patch at the beginning of the episode. Later seen at the girl's table in the cafeteria.
- "Bike Parade" - Seen in the crowd.
- "Shots!!!" - Seen in the cafeteria and in the rodeo arena.
- "Let Them Eat Goo" - Seen in the cafeteria.
- "Tegridy Farms Halloween Special" - Seen at the school assembly.
- "Board Girls" - Seen at the school assembly and at the Board Girls Gaming Club.
- "Basic Cable" - Seen in the school bus.
- "The Pandemic Special" - Seen in quarantine at school with the other students.
- "Pajama Day" - Seen wearing her pajamas on Pajama Day.
- "The Big Fix" - Seen in the school bus.
- "Back To The Cold War" - Evacuated into the South Park Elementary Gymnasium with the other children.
- "Credigree Weed St. Patrick's Day Special" - Appears at the school lobby, witnesses Butters getting arrested for sexual harassment. She is seen wearing a red shirt imprinted with a clover for St. Patrick's Day.