Beatrice is the source of redemption that exists. Dante struggles to find his spiritual identity. Dante casts Beatrice as the representation of divine love. She is the source of earthly goodness who expresses worry and concern for his journey. While she has died, Dante is able to use her image as a representation that good does exist. Dante has Beatrice implore Virgil to guide him because he is lost. In order for him to embark on his pilgrimage, Virgil assumes his guide because Beatrice has begged him to do so.
Beatrice is the embodiment of that which is pure and a love that is transcendent. She is both of this world and beyond it. Beatrice is the representation of what is possible. Amidst the sin and transgression that exists in the Inferno, Beatrice stands apart from it, literally, as a reminder to Dante that there can be unity and symmetry in this life. Beatrice displays concern for Dante, and this is a source of strength for him. It enables Dante to have courage to face what he will in the Inferno. In this world of sin and transgression and having the courage to boldly face it, Beatrice's name will not appear again. Just as no one mentions the name of Christ, Beatrice's name is too honorable and too redemptive to be present in the Inferno. Her role in the Inferno phase is to remind Dante to have the courage to face what he must. She has intervened to save Dante, and to transform him into a "pilgrim." Dante hears Virgil's story and is inspired to continue the journey. However, he also understands that no matter what demons he will face in his journey, the presence of Beatrice is what will provide the proof of goodness that exists in the world: Beatrice in this world, Christ in the next. She was of this earth. She is gone now, but Dante's love for her is eternal. It is in this condition that he sees his love for her as "La Vita Nuova" (The New Life). Her love is transcendent, and representative of a "new life." For Dante, this is what proves that there is virtue and vice, and those who fail uphold the former must do penance. If God can be merciful enough to create a Beatrice, then his goodness and "justice has to prevail."
It is a matter of opinion as to whether her presence detracts from the narrative. I think that Beatrice's presence is needed because it is a reminder to Dante that all is not lost. His "being lost" is a condition in which Beatrice saves him. The love they share is "a new life." It breathes vitality in a condition that is largely devoid of it. The inferno is such a sad collection of souls that Dante, the pilgrim, shows empathy for those eternally damned. Yet, Dante has to have faith in the divine plan and the God that exacts such justice because he has constructed goodness in Beatrice. She exists. She is the reason for unity and symmetry. In the Paradiso, Dante sees the face of Beatrice as that which fuses all the opposites together. In Beatrice, Dante sees the reason for goodness and virtue in this life. To honor God in the best way possible for what he has done in Dante's life in creating a Beatrice, there has to be absolute faith in surrendering to God's justice. Beatrice's presence as a woman that Dante knew personally helps to enhance Dante's strong faith in God. Goodness does exist because she does.