Isabel was a young woman with green eyes and red-brown hair which she kept in two pigtails. Prior to joining the Scout Regiment, her typical attire consisted of a simple buttoned tunic with a vest and knee-high boots. She also wore a small necklace with a ring tied to it, even when wearing her uniform. She is portrayed wearing a large orange button up shirt with the sleeves rolled up brown tights, and small tan boots with no necklace.
Isabel was shown to be an energetic, outspoken young woman rarely afraid to speak her mind. She was confident in her abilities, and the most cheerful of her companions. She was quite headstrong, shown when she continued to struggle and insult the Scout Regiment after she was initially captured. Isabel was also quite prideful, as she once stubbornly refused to tell Levi and Furlan the reasons she came back home beaten with one of her pigtails chopped off.
Isabel apparently did not know how to do math as she stated that it was not as important as feeding yourself in the underground. She valued Levi as a brother figure and became emotional if he berated her. She takes his opinions very seriously, as shown when she cried when he said she was an idiot for not knowing how to do math and continued to cry until he ruffled her hair.
Isabel proved to be a good horseback rider and was able to switch from using her omni-directional mobility gear to riding a horse with ease. She claimed she was good with animals, and something she had trouble with was humans.
After finding an injured bird, Isabel tried to return it to the surface so that it would be able to fly freely, rather than be confined in the Underground. She tried to sneak past a checkpoint to the surface without paying, but was found out and forced to flee. She eventually arrived on the doorstep of Levi Ackermann and Furlan Church, who chased off her attackers and saved her. Isabel, impressed by her saviors, asked to join their gang, and they agreed on the condition that she be trained to use ODM gear.
After Isabel had learned to properly use her gear, the three found an opening in the top of the Underground that led to the surface, and released the bird. While returning to their hideout, they were contacted by Nicholas Lovof, who offered to guarantee them safe passage out of the Underground if they assassinated Erwin Smith, a member of the Scout Regiment.
In order to lure out the scouts, the three decide to perform a heist using their ODM gear. Although they initially only get a response from the Military Police Regiment, they are eventually set upon by a squad of Scout Regiment soldiers. The trio split up to try to avoid capture, but Furlan and Isabel are quickly apprehended.
The two are brought by their captors to Erwin, who has also detained Levi. Erwin begins questioning them about their skill with ODM gear, but the three refuse to talk. It is only after Miche Zacharius begins physically harassing Levi that Furlan acquiesces and explains that they are self taught. Impressed, Erwin offers them a chance to join the Scout Regiment and Levi begrudgingly accepts on their behalf.
Isabel and her comrades are introduced to the rest of the Scout Regiment and assigned to Flagon's squad. As they are shown to their bunks, Isabel is appalled to learn that the scout's rooms are segregated by gender, and that she will not be able to stay in the same room as Levi and Furlan.
During training, Isabel demonstrates an aptitude for horse riding, impressing her fellow soldiers. She claims to be able to understand the horse, and that it has taken a liking to her. After their training, Isabel and Levi act as lookouts outside of Erwin's office while Flagon attempts to find Lovof's documents inside of it. Nothing is found, and they are forced to give up searching as Erwin arrives.
Furlan theorizes that Erwin is carrying the documents on his person at all times to ensure their safety, and suggests forcibly taking the documents and killing him during a scouting mission. Levi agrees to the plan, but orders to Furlan and Isabel to find an excuse to get out of participating in the scouting mission, fearing for their safety. Isabel and Furlan are both upset by the decision, insisting that they would rather leave the walls with him than return to the Underground, and convince him to allow them to participate.
The next day, the Scout Regiment embarks on its 23rd Exterior Scouting Mission. As soon as the scouts exit the gates of Wall Maria, the trio are left awed at the sight of the open world beyond the Walls. Their reverie is cut short by an encounter with Titans very early into the mission. Isabel acts as bait for one of the Titans while Furlan finishes it off.
A heavy rainstorm soon begins, and Levi decides to use the cover provided by the rain to assassinate Erwin. Not wanting their absence to draw the rest of their squad's attention, Furlan and Isabel agree to stay behind. Immediately after Levi leaves, Isabel and Furlan are ambushed by an Abnormal Titan, which quickly kills both of them.
Isabel, along with Levi and Furlan, stole omni-directional mobility gear while living in the Underground City. They trained themselves and in time became proficient with it. They were so good that they could evade the Military Police easily, and they looked at it almost like a game.
- Levi - Levi found Isabel among some garbage in the underground prior to the beginning of the story. After that, the two grew so close that Isabel saw Levi as a brother figure, often calling him 'aniki' or 'Levi-aniki,' meaning older brother. Levi was extremely protective toward Isabel, even willing to kill some people who had harmed her and cut her hair. Isabel tended to take any criticism Levi sends to her very seriously, showing how much Levi's opinion mattered to her. When Isabel died, Levi was devastated by the loss of his only friends and blamed himself for their deaths.
- Furlan Church - Having nearly opposite personalities, Isabel and Furlan were often seen at odds with one another. Furlan was calm, level-headed, and knew when things were serious. Isabel, on the other hand, was incredibly hyperactive, persistent, and tended to lose focus easily. Often, Furlan would lecture Isabel or try to be the voice of reason. Despite that, they were close friends to each other and Levi. In their first battle against a Titan, the two were shown to be cooperative and synchronized in their attacks, showing that the bond between them was strong. Isabel died trying to give Furlan time to escape the Titans, and her death made him stop running and face the Titans.
- Isabel's name has Hebrew origins, and means "God's Promise." Her surname is a reference to the Magnolia family of flowers.
- Isabel refers to Levi as "nii-chan/san" (aniki in the anime) which means "older/big brother" in English. While they are not related, it is common in Japan to refer to a slightly older male you respect or are close with, as "nii-san."