Sybelle is a twenty-five year old American who is a talented classical pianist. She is described as having long blonde hair. She and her caretaker Benji find Armand after he is badly burned from exposing himself to the sun after he attempts suicide after seeing Veronica's Veil when Lestat returns from his journey in Memnoch the Devil.

Sybelle is left traumatized in the care of her abusive older brother Fox after they are orphaned when their parents are killed in a car accident while traveling in Israel for Sybelle to perform piano, an event she feels responsible for. Her brother purchases Benji to be her companion to watch after her, and the three live in a large apartment in a hotel in New York. Sybelle compulsively plays the Appassionata by Beethoven, the piece she intended to perform on the trip where her parents died, and is unable to do other basic tasks without Benji's help.

When the abuse culminates to the point where Sybelle's brother is about to kill her, Armand, though not understanding exactly how, diverted his flight to his intended death to kill him, freeing Sybelle and Benji from his control. Benji and Sybelle rescue Armand from where he has landed on the roof, and are unafraid of his grotesque appearance.

After Sybelle and Benji help Armand recover, the three form a family, Sybelle accompanying Armand and Benji on their outings to movies and shows in New York. Sybelle also enjoys watching Armand hunt, and Armand indulges her in all of her desires, wanting only to facilitate her happiness.

Armand returns to Lestat to try to see his memories of his trip to the crucifixion with Memnoch, and leaves Sybelle and Benji with Marius. Armand is convinced to tell the story of his life by David, and decides he will dedicate it to Sybelle, but asks David to change her and Benji's names when it is published. Returning to Marius's home, Armand discovers Marius has turned Sybelle and Benji into vampires against his wishes. Sybelle is happy with the change, and after talking with Armand returns to playing the piano, awakening Lestat from his slumber.

In Prince Lestat, Sybelle is living at Trinity Gate in New York with Armand, Benji, and Louis, and plays piano on Benji's radio show. When Antoine plays violin outside her window, Sybelle performs a duet with him, and Armand invites him to join the household. Antoine and Sybelle become a musical duo, and are frequently seen performing together at the Château de Lioncourt. In Blood Communion, she is with Armand in his apartments, comforting him with Benji after the assumed death of Louis and Marius.