What daughter of Minos helped Theseus kill the Minotaur?

The daughter of Minos who helped Theseus kill the Minotaur is Ariadne. In the myth, Ariadne falls in love with Theseus and provides him with a ball of thread to help him navigate the labyrinth where the Minotaur resides. This thread allows Theseus to find his way back after slaying the beast, leading to his successful escape from the labyrinth. Ariadne's actions are crucial in ensuring Theseus's victory, showcasing her intelligence and resourcefulness.

The other individuals mentioned in the options do not play a role in this particular myth. Proserpina is associated with the story of Persephone and the underworld; Phaedra is another daughter of Minos but has a different mythological story; Andromeda is linked to the tale of Perseus. Therefore, the correct answer emphasizes Ariadne's pivotal role in the narrative surrounding Theseus and the Minotaur.