Cause and Effect, my love.”
Persephone and her husband came from an older version of the Matrix and remained in it avoiding deletion and thus becoming exiles. Persephone had been the neglected wife of the Merovingian, who sought temporal company from beautiful patrons of Le Vrai restaurant.
Betrayal for The Merovingian
When Neo, Morpheus and Trinity came to the restaurant for the Keymaker and were ousted by the Merovingian; Persephone, angry with her husband, offered them her help, in exchange of a passionate kiss from Neo as she has not received one from her husband in a very long time. Trinity draws her weapon and orders Persephone to change her mind, but relenting at a warning from Morpheus. Neo then reluctantly kisses Persephone.
She declines her offer to help them due to Neo's unrealistic kiss until Neo offered one more with more will and feeling. After this, Persephone tells Neo and Trinity of the time that she and her husband arrived in the Matrix, commenting that the Merovingian was much like Neo at one time and she misses that part of him.
Persephone then led Neo to the Keymaker offering help. While trying to leave the chateau, the Merovingian discovered that the trio came to take away the Keymaker and discovered that Persephone betrayed him. After talking about the Merovingian's "meeting" with the woman in the restroom, Persephone left the scene only to leave the Merovingian to handle Neo and the others.
Encounter at Club Hel
Though the Merovingian was furious when he discovered her betrayal, it did not appear to have any effect at all on their marriage, as they are still seen together in Club Hel during the visit by Trinity, Morpheus, and Seraph looking for the Merovingian for information on Neo's whereabouts. After the Merovingian was threatened by Trinity to help them find Neo, Persephone persuaded the Merovingian to help them as she knows Trinity is in love with Neo and she would kill for him.
After telling them where Neo can be found, Trinity and the others leave the Merovingian and Persephone. Soon after, Niobe met her in the TV room, who was looking for Morpheus. Given Smith's statement that Sati is "the last exile" when meeting her, he may have also tracked down Persephone and turned her into a Smith clone during Revolutions.
Persephone's current fate is unknown as she is not with the Merovingian and his surviving Exiles sixty years later. It's mentioned that most of the Exiles have been purged by the Machines and this may have included Persephone.
Persephone is a tall intimidating woman with pale skin, black shoulder-length hair, and crimson red lips.
She wears a translucent white dress in The Matrix: Reloaded, and a red, very low cut leather getup in The Matrix: Revolutions.
Enter the Matrix
In Enter the Matrix, Persephone is also willing to kiss Niobe or Ghost, depending on which character the player controls, in the same way she kissed Neo.
In the theatrical releases she is portrayed by actress Monica Bellucci.
The Matrix Online
In the Online game, she gives the Zion operatives the location of the Assassin's hideout during the critical mission, Death of a Destroyer. Beirn, one of Anome's lieutenants in Unlimit willingly betrayed his own leader and willingly helped the Merovingian because Beirn fancied her.
Her passion for poetry is also revealed in the final cinematic for Chapter 8, in which the Merovingian finds her reading Swinburne's Dolores and accuses her saying "more of your obsession?" causing her to walk out.
In Greek mythology, Persephone was the wife of Hades, the god of death. In the Matrix, Persephone is somewhat in a similar situation because her husband, the Merovingian, has control over death in a way by giving humans a chance to escape death and programs, a chance to escape deletion, thus making them Exiles. This may perhaps explain why Persephone is named after the Greek goddess.