Who is Ghanima Atreides from God Emperor of Dune and what is their importance?

Ghanima Atreides is the God Emperor Leto II's twin sister, Ghanima dies after a normal lifespan and is mourned by her brother. The rebels perceive his love for her as a defect by which he can be defeated. Ghanima bears children in Leto's name by Harq al-Ada. Leto intends to use Ghanima's water rings during his wedding to Hwi Noree, but bows to his mother Chani's wishes to use hers instead.