Janni appears to Nemo on his deathbed but refuses to follow in his name, instead choosing to run away so as to start a new life. (Nevertheless, she still accepts a specialty flare gun from Ishmael to summon the Nautilus if needed.) She stows away on a ship to London and takes on the name "Jenny Diver" when she finds employment in a wharf-side hotel. However, things take a turn for the worse when Janni is gang-raped by a collective of drunken patrons. Broken down, Janni summons the Nautilus.
Painting it black and nailing Nemo's skull to the forecastle as per her father's final orders, Janni leads the Nautilus to destroy every building on the wharf-side save for the hotel. Now assuming the role of Captain, Janni directs her crew to slowly and painfully slaughter the hotel patrons. (While she effectively killed her rapists and several other unpleasant individuals, many rather unfortunate innocents were also caught in the crossfire.) Before departing, she crosses paths with Mina Murray and leaves her, saying she has her respect borne from her father's immense contempt for the woman.
Nemo: Heart of Ice
Janni reappears in 1925 and still is conducting raids, including her raid on Ayesha's ship and theft of her treasure. Now assuming the name "Nemo", Janni conducts an expedition to the Antarctic in a repeat of her father's journey that led to his madness. She loses many of her crew in the process, but is saved from being killed thanks to her crewman and future lover "Broad Arrow" Jack and S. F. X. Van Dusen. Through the ordeal, she finds herself essentially becoming her father once more by literally going down the same path as he did.
In her first appearance, Janni is an estranged daughter to Nemo who rejects his habits and seafaring in the hopes of reclaiming a different life. However, following her gang-rape, she became very vengeful and succumbed to the very nature she sought to avoid. This led to mass murders of guilty and innocent alike, all dying by her hand and her crew.
But even after her corruption and adoption of her father's vessel and name, Janni still has honorable qualities. She respects her crew and is saddened by their respective deaths in the events of Nemo: Heart of Ice. There is also her eventual love with Jack to consider, which led to marriage and children. It is shown in her final (chronological) appearance in Century: 1969 when she rejects Mina's offer of bathing in the immortal fires so that she may one day be reunited with Jack.