Gabrielle was born sometime around 1730 and grew up in Naples. Judging from the fact that she is well-educated and could read even as a mortal, and that she marries a nobleman, she must have been from a noble family herself. Sadly, the French nobility that she married into had no money and lived in a crude style far removed from the Italian elegance that she must have been accustomed to. The Marquis de Lioncourt himself is not very well educated, and the marquise must escape into the world of books and letters to even tolerate each day. Her youngest son Lestat is her only real solace, and even though she is distant, not liking to touch or be touched nor be called "Mother," she does make an effort to talk to him occasionally, which is more show of affection than she is generally known to show. Whenever Lestat gets into his scrapes, it is Gabrielle who quietly but firmly lends him her support.

One time, Gabrielle tells Lestat that she is dying of TB, and confesses to him how utterly terrified she is of death. Compounded into that fear is her frustration that she had been forced to spend her life encarcerated within not only the physical confines of the castle, but the constricting behavioral code of the day which dictated what she as a woman, wife and mother could and could not do. Gabrielle urges Lestat to leave Auvergne, to go to Paris with Nicki and seek out his dreams. Only with the knowledge that he is safely away from this old world can she die in peace.

Lestat follows her advice and Gabrielle contents herself in receiving letters telling her of his successes. Right before her death, though, she decides to see her son one more time and travels to Paris, only to discover that her son had been somehow transformed into a nonhuman creature. Unable to deal with losing Gabrielle, Lestat offers the Dark Gift to her, an offer which Gabrielle instantly accepts.

The vampire blood instantly brings youth back to Gabrielle's body. Quickly throwing off her cumbersome female clothes, she transforms herself into a beautiful youth, choosing to wear the more mobile male clothing. She rejoices in her freedom, mentally and physically, something which she never was able to do in her mortal life. Intent on breaking free from her old life, Gabrielle cuts her hair; only to find it all grown back during her sleep. This sends her into utter panic, for the weight of immortality suddenly strikes her. The incident, though, is the only one of its kind. Once she has calmed down, Gabrielle never again shows any regrets or doubts about her new state of being.

For their remaining time in Paris, Gabrielle joins Lestat in his fight against Armand's "Children of Darkness" coven. After all that business is settled, she and Lestat leave Paris together to travel throughout Europe for several years. Through their travels, Gabrielle gradually leaves Lestat for longer periods of time, so that she may go off and explore the uninhabited wilderness. Unlike her son who keeps in touch with current happenings in France, including how his father and brothers are doing, through correspondence with his lawyer Roget, Gabrielle has no interest in maintaining even the appearance of having ties with the living.

Around 1789, Gabrielle and Lestat reach Cairo, where they are told of the outbreak of the French Revolution, the deaths of Gabrielle's sons, and the emigration of the Marquis. Although Gabrielle tries to convince Lestat to join her in the jungles and to forget all this, Lestat refuses to follow and instead insists on going over to the New World himself to take care of his father. Saddened but not about to change her mind, Gabrielle quietly leaves Lestat. As she parts, she makes Lestat promise her that if he should choose to end his being, he will seek her and they will come together again.

Gabrielle disappears from sight at this point and, other than that she roams jungles and sparsely inhabited regions, her activities are completely unknown for the next two centuries. Then in 1984, she pulls up in a red Porsche before Lestat and Louis, who are being attacked by angry young vampires and are trying to get away from the concert arena. Lestat is ecstatic about seeing his mother again, but before they can fully savor their reunion, that very dawn Lestat is kidnapped by Akasha. Gabrielle joins the remaining vampires at the Sonoma compound to await Lestat's return, withdrawn and uncommunicative, only concerned with Lestat's safety.