has more history than merely LOTR. She is in the Silmarillion and in Unfinished Tales. To claim she is power hungry seems a bit harsh based on one moment in the book (or the film).

Some evidence to the contrary -

"So it came to pass that when the light of Valinor failed ... she joined the rebellion against the Valar who commanded them to stay; and once she had set foot upon that road of exile she would not relent, but rejected the last message of the Valar, and came under the Doom of Mandos. Even after the merciless assault upon the Teleri and the rape of their ships, though she fought fiercely against Fëanor in defence of her mother's kin, she did not turn back." --Unfinished Tales, "The History of Galadriel & Celeborn"

"Then Galadriel spoke to Melian of of the Silmarils, and of the slaying of King Finwë at Formenos; but still she said no word of the Oath, nor of the Kinslaying, nor of the burning of the ships at Losgar. But Melian said: 'Now much you tell me, and yet more I perceive. A darkness you would cast over the long road from Tirion, but I see evil there, which Thingol should learn for his guidance.'
'Maybe,' said Galadriel, 'but not of me.' --The Silmarillion, 'Of the Noldor in Beleriand.'

"Galadriel counselled that the Three Rings of the Elves should be hidden, never used, and dispersed, far from Eregion where Sauron believed them to be. It was at that time that she received Nenya, the White Ring, from Celebrimbor, and by its power the realm of Lórinand was strengthened and made beautiful; but its power upon her was great also and unforseen, for it increased her latent desire for the Sea and for return into the West, so that her joy in Middle-earth was diminished. --Unfinished Tales, "THG&C"

see also- her protecting the third age as Sauron is rising to power --"Of the Rings of Power and the Third Age, The Silmarillion, and Unfinished Tales, "Cirion and Eorl"

Instead of someone power hungry, I see a very wise woman, one who stands by her word and does not waver. She maintains decorum in the face of many who do waver and are unsure.