Galadriel

Lady Galadriel is a major character in the Middle-Earth Film Saga and appears in all six. She is the mother of Celebrian, wife of Celeborn and grandmother of Elladan, Elrohir and Arwen.

Galadriel is a supporting character in The Lord of the Rings films and The Hobbit trilogy.

Background
Galadriel was born in Valinor during the Year of the Trees, a time before the First Age began and before the Sun was created. Galadriel left Middle-earth, after swearing no oaths. Galadriel was separated from her friend Feanor and travelled with Fingolfin, not taking part in the Kinslaying at Alqualonde. Living in Beleriand, Galadriel and Celeborn met each other after spending time in Thingol's court. She became very close friends with Melian the Maia. Later, Galadriel married Celeborn and they had a daughter named Celebrian. In the second age, Galadriel received one of the Three Rings of Power, along with Gil-galad and Cirdan. She was very conscious of Sauron's powers, and even knew that Annatar could not be trusted and was revealed to be SauronShe never used her ring when Sauron had it, but after he was defeated, she continued to have the use of her powers, the Ring of Adamant. Galadriel later became the mother-in-law of Elrond and the grandmother of Elladan, Elrohir, and Arwen.

The Lord of the Rings
Her role in the film plays out similarly to the novel.

The Hobbit trilogy
Though not appearing in the novel, nor being mentioned, Cate reprises her role for The Hobbit trilogy.

In An Unexpected Journey, Galadriel appears in Rivendell, where Gandalf is surprised to see her after being summoned by Saruman, the wizard Galadriel hardly touched. She was the only one who believed Gandalf's claims. She claims to know that Gandalf sent the dwarves and the Hobbit on their way, but the two of them keep it a secret.

Before leaving, Galadriel tells Gandalf that he is right to help Thorin Oakenshield, but feels there is a darkness kpet at bay. Gandalf reveals that he brought Bilbo to the quest because of the courage Bilbo gives. Galadriel tells Gandalf that whenever he needs her, she will come to him.

Trivia

 * Galadriel is one of the three main characters to appear in all six of Peter Jackson's Middle-earth films, along with Gandalf and Sauron.