What is the name of the Hawaiian volcano goddess's sister?

The name of the Hawaiian volcano goddess's sister is Hiʻiaka.

Hiʻiaka is best known as Hiʻiakaikapoliopele, meaning “Hiʻiaka in the bosom of Pele.” In Hawaiian tradition, Pele carried her sister to Hawaiʻi in the form of an egg, a story reflected in the name Hiʻiaka, commonly interpreted as “carried embryo.” Hiʻiaka is associated with hula, chant, sorcery, healing, and the fertility of the land.

Her most famous legend sends her from Hawaiʻi to Kauaʻi to retrieve Pele’s beloved, the chief Lohiʻau. During the dangerous journey, Hiʻiaka battles supernatural beings, revives Lohiʻau through prayer and chanting, and returns with him. In several versions, Pele’s jealousy leads to the destruction of Hiʻiaka’s sacred lehua grove and the death of her friend Hōpoe.

A common mix-up is treating Hiʻiaka as Pele’s only sister. Hawaiian traditions name multiple sisters, including Nāmaka, Kapo, and other Hiʻiaka figures, but Hiʻiaka is the canonical answer to this quiz question.