Gabriel is the younger sister of Setsuna Mudo, who was also known as the reincarnation of the soul of the former Great Cherub, Gabriel. Gabriel had been one of the Four Elemental Angels, specifically the Angel of Water, and she had vocally opposed Sevothartes violent actions while serving as Prime Minister. In order to remove her from his path, Sevothartes paralyzed her with a needle and sent her soul to Earth where she would unwittingly serve him as Setsunas guardian angel.
When Sara died, her soul was taken up to heaven by Zaphikel for study of its unusual spiritual energy signature. Metatron removed the needle from Gabriels back and Saras soul awakened in it. She initially awoke blind but was later healed with Gabriels water powers which helped Raphael revive Setsuna. Sara is deeply in love with Setsuna.
Raphael claimed to love her, but through Sara, he came to realize that his true love was someone else close to him. Despite having a pure and innocent heart, Sara possesses a fierce temper and sharp tongue.