Guinevere makes her first appearence in Season 2 after her half brother, Odysseus eu Britannia, failed to have a political wedding with Empress Tianzi the Empress of the Chinese Federation. She regrets that the failed wedding as an insult to the First Prince, believing that retaliation was in order, though Odysseus personally does not feel offended and hoped Tianzi was unharmed. Guinevere's comment proves to be a little more than an idle threat, as the Britannian Prime Minister, Second Prince Schneizel el Britannia, decides that no action should be taken against the Chinese Federation for the time being.
One month after the Second Battle of Tokyo and the disappearence of the Emperor, Charles zi Britannia, Guinevere appears in the Imperial Court when Lelouch declares himself the 99th Emperor of the Holy Britannian Empire after killing Charles. Guinevere then orders the Royal Guard to execute Lelouch for doing so. Suzaku appears and stops the Royal Guard, Lelouch then used his Geass to command the Imperial Court including Guinevere to accept Lelouch as their new Emperor. She is then employed as a maid along with Princess Carine le Britannia. Her fate after the F.L.E.I.J.A.'s use on Pendragon is unknown.