Florencia is the first wife of Sylvester, the archduke of Ehrenfest. She is the biological mother of Wilfried, Charlotte, and Melchior, and later becomes the adoptive mother of Rozemyne. Her background is that of an archduke candidate from the neighboring duchy of Frenbeltag, born as the daughter of the previous Aub Frenbeltag and his third wife. As she had an older brother who was favored to inherit, Florencia was expected to make a political marriage. She entered the Royal Academy at age ten, where she met Sylvester, who was two years younger. Despite it being very rare for a noblewoman to marry a younger man, Sylvester fell in love with her and went to great lengths to persuade her and her family to accept his courtship, eventually winning approval to escort her at her graduation ceremony.

In terms of appearance, Florencia has indigo eyes and straight, light-blonde hair that is close to silver in color. She has a peaceful smile and gives the impression of a gentle, refined beauty. However, her personality stands in contrast to this demure appearance. Florencia has a cool head and a firm attitude, and is a strict, no-nonsense mother. She is one of the few people who can keep tabs on both her husband Sylvester and her son Wilfried, and is also capable of holding Ferdinand accountable. Even when deeply upset or angry, she can maintain perfect composure.

Florencia's motivations center on the welfare of her children and the stability of Ehrenfest. After marrying Sylvester and moving to Ehrenfest, she was immediately ostracized by her mother-in-law Veronica, who was harsh on outsiders. She found sympathy and support with Elvira and joined her political faction, which came to be known as the Florencia faction due to her higher rank. When her first child Wilfried was born, Veronica claimed it would be dangerous to trust the child to someone who had just married into the family, and as a result Florencia was denied control over her son's upbringing. She was only able to see him briefly during family dinners, and because her time was so limited, she did not realize that Wilfried's education was going very poorly. Satisfied with her control over Wilfried, Veronica had no interest in Florencia's other two children, Charlotte and Melchior, allowing Florencia to raise them with the love and strictness needed to become proper archduke candidates.

Florencia plays a significant role in the story when Rozemyne joins the family. She welcomes Rozemyne with open arms as her adoptive daughter, helps her gather donations for the Hasse monastery, and assists in planning the charity harpsiel concert. When Rozemyne suggests that she and Wilfried swap places for a day, Florencia is dismayed to realize how serious the problems with her son's education truly are. She becomes coldly furious, blaming Sylvester both for allowing her to be cut off from Wilfried's upbringing and for the dire consequences of her absence. She excoriates Wilfried's retainers for their failure and is the first to agree with Rozemyne's suggestions for improving his education. Recognizing that continuing to coddle Wilfried would be truly cruel, she works to implement the new curriculum and is deeply thankful to Rozemyne for helping save her son's future.

Over the course of the story, Florencia shows considerable development. When Wilfried later commits the crime of entering the Ivory Tower, she is anguished as his mother, knowing she can do little to protect him. For the first time, she tells her son how Veronica stole him away from her right after he was born, and tearfully explains how serious his situation really is. She is overwhelmed with relief when Rozemyne successfully negotiates to reduce his punishment. She also becomes involved in interduchy relations, helping to fill chalices for her home duchy of Frenbeltag by taking mana from the imprisoned Veronica. Despite having a hard time turning down requests from her older brother, the current Aub Frenbeltag, she works to balance her family obligations with her duties to Ehrenfest. She later gives birth to a daughter named Henrietta.

Notable abilities of Florencia include her talent for managing people, particularly her ability to control Sylvester and provide appropriate advice to Ferdinand. She is skilled in political maneuvering, working with Elvira to gather information and conceal her dislike of troublesome visitors such as Georgine. She is also capable of taking over her husband's duties when necessary, such as reading and responding to letters from their children. Her composure under pressure is a significant ability, allowing her to maintain proper noble decorum even in highly distressing situations.