Genevieve Dieudonné was a female vampire of the Lahmian bloodline in the World-that-Was. Considered (even if grudgingly in some circles) a heroine of The Empire she became the lover, companion and later wife of the actor, poet and playwright Detlef Sierck.
As a vampire, Genevieve appeared as she had when she had breathed her last, a lovely young woman of sixteen years of age with a slim figure and blonde hair. She retained a trace of a Bretonian accent, which could become more prominent when she was emotional. Her Lahmian bloodline meant that her predatory nature was less obvious than many vampires but if her control slipped her face transformed and her teeth and claws emerged from their sheaths. She often wore smoked glasses if she was active in daylight.
Genevieve Sandrine du Pointe du Lac Dieudonné was born in 1842 IC[*] in the city of Parravon. Her father was a minister of the ruling family and she had several sisters, one of whom, Cirielle lived into her sixties.[1a]
During the following centuries she travelled to Araby and the Far East. For a century she sailed between Cathay and Nippon. Genevieve learned Cathayan and met Master Po, with whom she would spend three decades of her life. He told her local tales and taught her some minor magic as well as facets of Cathayan culture. 
For several decades Genevieve worked as a tavern wench in the Crescent Moon in Altdorf. In 2480 she was approached by Prince Oswald von Konigswald who persuaded her to join his quest to sneak into Castle Drachenfels and slay Constant Drachenfels. The success of their quest made her famous.[1a]
Genevieve travelled to Middenheim and found employment with the Temple of Ulric as a prostitute/spy, sweetening up foreign guests in the city for the Festival of Ulric. She was performing her duties when she was captured by the Guardians of Purity part of the Moral Crusade led by Claes Glinka. She escaped the slavers of Dien Ch’ing, a sorcerer and cathayan cultist of Lord Tsien-Tsien (Tzeentch), to whom she and the mercenary Vukotich had been delivered and was instrumental in exposing the machinations of Chaos behind the crusade, killing Lord Marshall Blasko and revealing Glinka to be a mutant. Luckily Prince Oswald’s father recognised her and was able to vouch for her.
Afterwards, tried of the adulation and suspicion of mortals she decided to withdraw from human society, retiring to a convent of the Order of Eternal Night and Solace where her grandsire, Lady Melissa d'Acques was also residing .[1b]
In 2505 a restless Genevieve decided to return having been invited to the premier of the theatre play Drachenfels. She travelled to Altdorf on the riverboat the Emperor Luitpold on which she had brief fling with Ambassador from Kislev, Sergei Bukharin before she was reunited with Prince Oswald.[1c] There she met Detlef Sierck, with whom she fell in love and together they would manage to defeat the Great Enchanter for the last time at Castle Drachenfels.[1d]
Saving the life of the Emperor meant that Genevieve was created a Heroine of the Empire which gave her some official protection and also enabled her to remain in Altdorf with Detlef. As time passed she grew more and more concerned that she was a danger to her lover and following the revelations of the Trapdoor Demon she left him. His grief at their parting would spur him to write his third group of poems in the sonnet, To My Unchanging Lady, dedicated to Genevieve. 
She travelled to Tilea and became trapped within the strange enchantments of the House of Udolpho from which she barely escaped with the aid of the revolutionist Aleksandar Kloszowski whom she accompanied back to the Empire.  The spymaster Mornan Tybalt, the Keeper of the Imperial counting house then ensnared her in Middenheim using her association with Kloszowski. He threatened her with being imprisoned in silver shackles in Mundsen Keep as well as ruining Detlef and so with his agent Balthus she was sent to kill Graf Rudiger von Unheimlich. 
Following these and other adventures she returned to Altdorf and Detlef, arriving shortly after the implementation of Clause 17 of Antiochus Bland’s Sanitation Bill which called for the burial or burning of all dead bodies - undead heroines of the empire included. With the aid of her grandsire who had in fact summoned her to the city for the purpose, the lovers foiled the assassination of Bland and following his unusual incapacitation, the revocation of Clause 17 was quietly implemented. 
Detlef and Genevieve were married shortly after. 
The End Times
Like Constant Drachenfels, Genevieve is never named in the End Times books, but just like her old adversary, a compelling argument can be made for her appearance. First of all in Warhammer: Nagash, a vampire messenger appears to Balthasar Gelt who not only bears an uncanny resemblance to Genevieve but also hails from Parravon. She passes her message, apparently from Neferata about who she states "I am no fonder of her than she is of me, but strange times make for stranger alliances." In Warhammer: Archaon she appears again on behalf of Neferata with a message and warning for Vlad von Carstein before she goes to meet her own fate "My time in this world is coming to an end, just as yours is, and I think I would rather meet in my homeland."
Genevieve received considerable fame and notoriety as a Heroine of the Empire and had songs, stories and plays written about her. She even published her own biography, A Life.
The Song of Bold Oswald and Fair Genevieve was written after her first encounter with Drachenfels and suggested that the Prince had confronted the Great Enchanter for the love of his long dead lady. [1c] . Detlef himself greatly contributed to her fame with the ill-fated play Drachenfels, which he later rewrote as The Tragedy of Prince Oswald , Genevieve and Vukotich, and also his infamous and later suppressed sonnet cycle To My Unchanging Lady.[1e]
As a vampire of not inconsiderable age, Genevieve was considerably more resilient, faster and stronger than humans – for instance she could crack an iron shackle with one hand. She did not burn in daylight, but it did make her weaker, tired and on occasion her eyes stream – she cast no reflection and silver burned her. [1e] During her time in Cathay she learnt some minor magical charms and some hand to hand techniques. Fire is dangerous - she was thrown into a bonfire in the Black Mountains and it took ten years to grow all of her skin back.
*: Warhammer Companion reports that Constant Drachenfels was defeated by Oswald in 2480 ICNeeds Citation; Genevieve remembers that she was born 638 years earlier and that she was 12 years old when Drachenfels marched upon Parravon[1a], which would place the year of her birth in 1842.