Can someone explain to me why people think Galadriel is acting out of character?
Tolkien always said she was an arrogant, ambitious spitfire before she settled down in Lothlorien. Hell, she was still leaving Celeborn for centuries at a time to adventure. That's the whole reason that "passing" her test when Frodo offered her the One Ring was such a big deal. Young Galadriel would have taken it without question or hesitation. She proved that she had grown.
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Also, even if they deviate from the source material... that's still mission accomplished for Tolkien. His primary goal was to create a mythology. And any successful mythology is retold. And they diverge from the original telling in the retelling. Even Tolkien himself was constantly reinventing his stories, to the point where the most recent versions constantly contradict each other.