My guess is that they want to portray a modern character transformation in the series, as has been the recipe for success in many a modern film adaptation: from a young, angry teenage
Galadriel, confused and blinded by circumstances, to a wise, mature and good-natured Galadriel, as she is known and could be considered a powerful role model.
This ambition is fine in principle, but there are a few problems:
1 - (especially for
Tolkien fans) It doesn't fit the
books, doesn't fit her age, and doesn't fit her role in the
Second Age.
2 - (for everyone) It's just extremely bad, implausible and bunglingly realized. You can only feel ashamed when you see it. You hate her. She has a miserable character and is vicious.