Jeanne is an Umbran Witch, sharing many of the same powers and abilities as Bayonetta such as summoning demons and slowing down time. Like Bayonetta she wields four specially-crafted and enchanted handguns, collectively known as All 4 One, individually as Porthos, Athos, Aramis and D'artagnan, along with a Katana named Angel Slayer.
An enigmatic character, Jeanne reappears time and again to Bayonetta during her journey as both an ally and an enemy, prompting revealing and often seemingly conflicting details of their shared past. 500 years prior to the events of the game, Jeanne was participating in her final trial as heir to the throne of the Umbran Clan, and chose to disregard the laws and traditions so that she could challenge Bayonetta to combat. Despite losing this battle, Jeanne worked with Bayonetta during the Witch Hunts and against the Laguna, even during the siege of the Umbran sanctuary where Bayonetta's mother was slain. In the midst of the battle she drove a knife into Bayonetta's chest and sealed her away with a red jewel, placing her in a casket at the bottom of a remote lake where she would be awakened centuries later by Antonio Redgrave.
Jeanne's whereabouts were then unknown until she re-encountered Bayonetta in the present day, and near the end of their final battle and the climax of the story it was revealed that Jeanne and Bayonetta were far from enemies in the past; indeed, they had been childhood friends, and Jeanne had sealed Bayonetta away for her own protection. At some point after the event, she had been placed under the control of Balder, the last remaining Lumen Sage and the man who orchestrated both the war that destroyed his own order and the Witch Hunts that brought the Umbra to the brink of extinction. Freed from this control during her last battle with Bayonetta, Jeanne was seemingly killed by a barrage of missiles, and Bayonetta briefly mourned her old friend before setting off for the final battle.
In truth, Jeanne had survived, using the same gem that she had sealed Bayonetta away with to project a shield at the moment the missiles exploded and escaping mostly unscathed. Witnessing the aftermath of Bayonetta's battle with Balder, she rode her motorcycle on a haphazard dash up the side of the Creator's statue as it launched off into space, battling angels along the way and eventually managing to free Bayonetta before she could be absorbed by Jubileus in her awakening. While seemingly dispatched again, she lent her aid in the summoning of Queen Sheba and the final vanquishing of Jubileus, and then appeared before Bayonetta again, vowing to return her to the Earth alive if it was the last thing she did. She and Bayonetta set about destroying the remains of the Creator's statue as it drifted through the atmosphere, eventually falling through themselves.
Jeanne played along at Bayonetta's funeral, disguising herself as a nun and performing services to lure the Laguna in close before launching her attack on the angels in much the same way Bayonetta had in the opening. After some prompting from Jeanne Bayonetta sprung from her hiding place within her coffin and joined her friend in battle with the angels as the game drew to a close.
Through information provided in her weapons and alternate costume descriptions, it's learned that Jeanne is a schoolteacher and moonlights as a Super-Hero know as Cutie-J, wearing a platinum cat-like helmet with her Umbran battle uniform and wielding the Bloody Moon, an ancient Umbran weapon.
Jeanne is unlockable for play by clearing the game on Normal difficulty or higher with an overall Platinum trophy at the end. Alternately, one can enter a code and pay one million Halos for access to her. In practice, she plays much like Bayonetta, as she did when she served as a boss in the game. Important differences include the fact that Jeanne has her own lines of dialogue and voice during gameplay (though not in cutscenes), access to altered versions of Bayonetta's arsenal of weapons, and the ability to dodge back-to-back infinitely and do 1.5 times as much damage with all of her Wicked Weave attacks. This is offset by her inability to activate Witch Time through normal dodging- only through an exactly timed use of her Moth Within ability (or the various Accessories available from The Gates of Hell) can it be used. Jeanne also possesses various unique alternate costumes available only to her, and when acquiring a Platinum trophy at the end of a chapter has her own variant, showcasing herself instead of Bayonetta.