Grandmother (DE1a 25 first appearance) is old, wise and a bit kooky. The old woman simply called "Grandmother" is also a highly respected person in Valley of the Wind .
In the film, she has poor eyesight, lives in the castle and has watched Nausicaä grow up. Grandmother was the one told us about the legend of the saviour who will come to help mankind, and it is she realizes Nausicaä is the saviour. When the Valley forest was infested with Fukai poison, the people went to her for guidance. She decided that the only way to save the rest of the Valley was to destroy the forest.
In the manga, she's part of the group of wise women that Yupa brings Khotosh Herb for and later treats Yupa 's wound after Nausicaä's duel with the Torumekian Duelist (DE1 pg 66). She is known as the matriarch and is over 100 years old, the oldest person in the Periphery (DE1 pg 215).
a See Page Conversions Between Editions to convert Deluxe Edition volume 1 (DE1) to other editions