If I disregard the question of canonicity of
RoP trailer description of
Galadriel (or Waradriel, if you will - BTW, I never entirely liked Nerwen stuff, it seemed somewhat off to me), I would mention one issue I have with it, among others: how
boring it is. At least to me.
It's not that trailer describes her as powerful, but what kind of power it focuses on - mainly physical, sword-wielding. In LOTR
books, she is very powerful too, but it's different kind of power, not a brute force of a warrior. I would compare it more to Melian-like power. It is power of a will, ability to read hearts, that kind of stuff. There are not that many powerful characters in media with this kind of power. Certainly far fewer than characters of physical and warlike prowess.
It was immediately disappointing to see, how prominently they focus on Waradriel fighting-power. Maybe she will excercise that other type of power in RoP as well, but make no mistake, they primarily see Galadriel as Waradriel, otherwise this aspect of her character would not be featured so much in trailers. (For example,
Gandalf or
Elrond certainly had their fair share of
sword fighting, but it they released some trailers focusing on these characters and showed them prominently as sword-warriors, I would find it equally concerning. Because this is not what these characters should be mainly about.)
To me, it just makes her seem more
generic character. The fact that she is supposed to be driven by revenge only cements it. (First of all, it's dubious whether this could be considered canon. I know Galadriel loved
Finrod the most - after all, who doesn't?

- but that does not necessarily imply revenge wish.) But mainly - how many great fighters driven by revenge have we already seen in various movies? For me, far too many. Yes, they tend to be male, but simple gender swap does not make it any more interesting to me.
If a writer chooses this motivation, I consider it the most lazy and formulaic character writing. OK, I could understand it when they are adapting some source material, where this has already been well established about the character. But why would they do it when they don't have to? I can't wrap my head around it. It doesn't really add any depth to them any more, if anything, rather the opposite, IMHO.
And the worst part is that you already have a lot other stuff to work with character like Galadriel, even if you want to maintain "girl-power" aspect of her. You could for example explore, how was she influenced by
Melian, undoubtedly very powerful female character, more than her husband
Thingol, I would argue. You could explore Galadriel's ambition, desire to rule according to her own will, and how she learned from Melian how to excercise power even without resorting to physical fighting. That would be more unique take of a strong female character, I think, and it would
feel less like a deviation from the canon. (OK, to be fair, they most likely don't have rights to mention Melian in RoP, but it only shows what a bad idea it is to adapt
Tolkien when you only have rights to small bits and pieces of his lore.)