Isabella is the mother of Rovel and the paternal grandmother of the protagonist, Ellen, making her a key member of the Vanklyft family. As the matriarch of this noble house, which has a strong military background, she holds a position of authority and care over her family's domain. Her most prominent characteristic is her overwhelming enthusiasm and affection for her family, particularly her newly met granddaughter. When she learns of Ellen's existence, her excitement is immense, and she eagerly presses her son to arrange an introduction. Upon meeting Ellen, Isabella displays a dramatically warm and doting personality; she is overjoyed by her granddaughter, shrieking with delight at Ellen's shy attempt to address her as grandmother and immediately sweeping the girl into an embrace.

Her temperament, however, is not solely defined by effusive warmth. Isabella demonstrates a capacity for seriousness and a cold, sharp demeanor that strongly mirrors her son Rovel. When the discussion turns to matters of betrayal or threats against the family, such as the actions of a retainer named Albert, her expression becomes icy, showing she is a formidable woman who takes the security and honor of her house very seriously. This duality suggests a strong, protective matriarch who can be both a source of loving enthusiasm and stern resolve. Her role in the story is primarily as a supportive family figure who, along with her husband Lawrence, provides a safe and welcoming base for Rovel, Origin, and Ellen. The Vanklyft household greets the family with great enthusiasm, offering a place where they can reconnect with their human lineage and find safety away from the intrigues of the royal court.

Isabella's key relationships are central to her character. Her bond with her son Rovel is built on a foundation of pride and familial duty, though she does not hesitate to press him for what she wants. Her relationship with her daughter-in-law, Origin, the Spirit Queen, is one of startling acceptance; despite initial surprise that her son married a spirit, she quickly embraces the situation, celebrating that her granddaughter is destined to be the next Spirit Queen. However, her most significant relationship is with Ellen. Isabella is fascinated by her granddaughter, asking curious questions about the nature of her spirit heritage. She is deeply impressed and left speechless by Ellen's incredible power, which includes the ability to transmute charcoal into diamonds and produce gold bars at will. Her development largely revolves around moving from a distant relative by blood to an active and doting grandmother figure, fully integrating Ellen and Origin into the human side of the family. While Isabella herself does not display any notable supernatural abilities, her importance lies in her emotional support and her role as the human matriarch who anchors the family's noble lineage, providing a stark contrast to the divine and heroic nature of her son, daughter-in-law, and granddaughter.