Isabel is a precocious girl who is very creative and loves to draw and invent. She is also shown to love her older sister and spending time with her. Like another precocious Princess, Isabel values keeping promises no matter what to the point where she dislikes people breaking promises they made her. Also like Sofia, she loves doing her research and places a lot of faith in books she's read. Unlike her older sister, Isabel did not like Dia de los Muertos because it reminds her that her parents are dead until Elena explained why she loves it, also unlike Elena, Isabel is not into sports.
Isabel is a tanned skin girl with a slender figure and amber-brown eyes, much like her sister's. Being younger, she's shorter than Elena and has long dark brown hair tied back with a bright blue ribbon.
Her signature outfit is a bright blue dress with short puffy sleeves decorated in flowery patterns. Her skirt measures up to Isabel's knees and tied around her waist is a blue bow. Isabel wears white tights and black shoes with blue bows.
For formal occasions, Isabel is seen wearing a pink-and-yellow ball gown, with a yellow ribbon in her hair.
When the evil power-hungry sorceress Shuriki invaded the Kingdom of Avalor and murdered her parents, Isabel and her grandparents were placed inside an Enchanted Painting for their protection by Alacazar while her sister, Elena, ended up trapped inside the Amulet of Avalor when she confronted Shuriki alone. Forty-one years later, Isabel and her grandparents were released from the portrait by Alacazar's grandson, Mateo, and helped Elena defeat Shuriki and liberate their kingdom.
In the series that serves as the special's sequel, Isabel is a major character alongside with the rest of her family.
In "Model Sister" it is shown that Isabel's relationship with her older sister is becoming strained due to the fact that Elena's new role as the Ruler of Avalor has given her an extremely busy schedule. She is especially angry with her sister when she discovers that Elena has been ditching her to attend King Toshi's visit when she needed her help with her invention. Elena makes it up to her by getting her invention ready in time for the Inventor's Fair.
In "A Day to Remember", Isabel does not want to celebrate Dia de los Muertos since it reminds her that she no longer has her parents to turn to. Elena manages to get her to come by reminding her of all the happy times they had with their parents and why they celebrated the Day of the Dead. Feeling better, Isabel goes to the alter and puts a drawing of her parents on the alter alongside the food tribute.
In "The Scepter of Light", Isabel is looking forward to the Eclipse Festival and finds Armando's story about Orizaba highly amusing. During the eclipse, however, Orizaba is revealed to be real. When Elena and Mateo set out to defeat her and send her back, a concerned Isabel goes after her with Gabe. When they catch up to Elena, they accidentally ruin Elena's attempt to get rid of Orizaba by blocking out the magic light Elena is bathing the moth fairy in with the Royal Coach. It casts a shadow in the path of the light which restores some of Orizaba's powers. The moth fairy tries to attack Isabel, but Elena saves her by making their father's scepter glow so bright that the light defeats Orizaba. Elena then collapses to Isabel's concern. Isabel, Gabe, and Mateo take Elena back to the castle and put her to bed where she stays for the next two days. When Elena wakes up, she reveals to a relieved Isabel that she gained magical abilities while she was imprisoned inside the amulet their mother gave her on her fifteenth birthday and that their father's scepter is also magical.
In "Navidad", Isabel is looking forward to spending Nochebuena with her friend Cristina after her father invites them to their village for the evening. However, Elena receives multiple invitations from other people who want her to attend their Navidad celebrations. Isabel supports Elena's attempts to compromise and all the while Isabel makes a Navidad Pinata. However, Doña Paloma ruins her sister's attempt by making everyone competitive to the point where everything gets ruined, including Isabel's pinata. The disaster makes Fernando decide to take Cristina home, to Isabel's sorrow. Elena fixes everything with a parranda, to Isabel's joy.
In "Olaball", Isabel meets up with King Joaquin again and becomes fast friends with his daughter Princess Caterina. She takes Cat on a tour through town. In town, they are wowed by the Voladores and Isabel tells Cat how she has always wondered how the tower works. The next day, Cat takes Isabel to the tower. Despite her misgivings about it, Isabel rides with Cat to the top where they get stuck. Gabe gets them down.
In "Three Jaquins and a Princess", Isabel shows off her latest invention, only for an accident with it to annoy Esteban, who reprimands her, hurting her feelings. As a result, as Elena consoles her, Migs arrives with his new mate, Dulce, who soon lays three eggs that will hatch into their new children. After she leaves to find Anoki Berries for their babies to eat, the eggs hatch, and Migs leaves to go help her, while Elena tells Isabel to summon her for help if she needs it when Isabel offers to watch them for Migs and Dulce. However, Isabel soon learns how difficult it is to watch the babies as they grow restless and cranky without the Anoki Berries, and she is forced to chase one of them to the kitchen, just barely hiding it from Elena when she finds Isabel in the kitchen, and Isabel is forced to lie to her big sister to convince her everything's fine. However, when one of the babies drinks Mateo's Enlarging Potion and all three ruin the Bake-Off that Elena was judging, Isabel feels guilty over not telling Elena the truth that she was struggling with watching the babies, and after Elena voices her disappointment and anger with her little sister, working with Mateo, Skylar, and Luna, they are able to round the babies up and return the one affected by Mateo's Enlarging Potion to normal before Migs and Dulce return. Once they do, they and Isabel gives names to the babies, and after Esteban also makes amends with Isabel with helping her with her invention, Isabel is allowed to go play with Mingo, Zoom, and Estrella.
As Elena and the others prepare for the Jaquin Festival in "A Spy in the Palace", Isabel is with Mingo, Zoom, and Estrella as Migs, Luna, and Skylar are practicing their flyover for the ceremony. After they finish, Isabel offers to improve it by equipping them with her latest invention, Sky Painters. However, when Migs sees Skylar and Luna messing around with them, he changes his mind and quits. Isabel talks to him about how he'll let his cubs down if he doesn't perform in the flyover, convincing him to rejoin Luna and Skylar for the performance as they do their tricks before King Verago, Chief Zephyr, and other Jaquins in attendance at the festival. Isabel is unaware that Carla Delgado is with her big sister, in disguise as Armando's distant cousin Rita Perez, preparing to steal her mother's Carnaval Tiara for Shuriki.
- Isabel is an inventor just like Harley Diaz, Jenna Ortega's (her voice actress) other character in Stuck in the Middle.
- As of "Three Jaquins and a Princess", Isabel is eleven years old, so she is six years younger than Elena and chronologically fifty-two years old. This makes her Disney's third oldest princess, preceded by Elena and Kida from Atlantis: The Lost Empire.