Lillian emerges as a central figure in Jewel Land's narrative, initially positioned as a highly skilled candidate vying for rulership. Her background holds a profound twist: she originated not as a human, but as a doll once owned by Lady Diana. Abandoned when Diana departed the Jewel Palace, this doll became the subject of a bargain between the Jewelpet Luea and the antagonist Joker. Luea employed magic to animate the doll, naming her Lillian and implanting false memories to establish her as the adoptive sister of Prince candidate Cayenne. This artificial creation resulted in her illegal candidacy under the alias "Lady X."

Her constructed nature initially manifests in a calm, stoic, and emotionally reserved personality, often appearing distant or indifferent. This composure, paired with exceptional etiquette and academic prowess, cements her status as the top Petite Lady candidate. Yet, cracks in her perfection surface through unexplained memory lapses and an intense, almost possessive affection for Cayenne, whom she believes is her destined soulmate. This fuels a sharp rivalry with protagonist Momona, particularly over Cayenne's attention, revealing Lillian's capacity for bluntness and jealousy.

Lillian's character evolves through interactions. She gradually warms to Momona and the other candidates, shifting from a cold rival to a supportive figure who offers Momona guidance. Concurrently, she forms a deepening bond with Prince Miura. Their relationship progresses despite Luea's disapproval and the revelation of Lillian's true nature. Miura's unwavering acceptance culminates in a confession of love and their first kiss after her temporary disappearance and revival.

Key plot developments directly stem from her doll origin. She experiences mysterious fatigue and fainting spells upon encountering dolls or hearing a specific melody from Diana's music box. Discovering the truth—that Luea animated her to fulfill Joker's schemes and that her memories with Cayenne are fabrications—triggers a profound crisis. To shield Luea from the consequences of their actions, Lillian vanishes. Upon her return and acceptance by Miura, she confronts her existential reality, moving beyond her programmed purpose.

Her journey concludes with significant achievements, including participation in saving Jewel Land during its final crisis. In the epilogue, at Momona and Cayenne's wedding, Lillian catches the bridal bouquet—a symbolic act preceding her ascension as the new Lady Jewel, the ruler she aspired to become. Elena assumes the role of educator for future candidates.

Physically, Lillian possesses long purplish-black hair with straight bangs, typically adorned with a yellow ribbon featuring a diamond-shaped gem. Her distinctive attire includes a black dress resembling a half-buttoned tank top layered over a white blouse, accented by a purple butterfly motif on the collar. This incorporates a tutu-like skirt over a shorter black skirt, paired with black heeled sandals displaying the same butterfly design. Her formal Lady attire shifts to a purple and white dress with yellow accents, maintaining her signature hairstyle. Her narrative draws thematic parallels to the Pinocchio story, exploring artificial life seeking humanity and acceptance.