Ultimately, the point is that Rohirrim culture, as defined in the book, would lead her to particular character moments; but that the culture was subtly cherrypicked for the movie, and she ended up someplace different.

In the movie, (a) she gets a couple of "aint she some cunning" battle moments before her climactic battle and (b) in her climactic battle, her reactions are quite different. In the novel, she was essentially attempting suicide. The bigger and badder her adversary, the better, and she was glad to face something so terrifying. Of course, the movie couldn't leave that the same, or else she'd have willingly been squashed by the first elephant she met.

I haven't found anything yet on the weeb discussing Eowyn's combat experience or lack thereof, but I did find this interesting commentary at the Encyclopedia of Arda regarding our discussion of the importance of the omission of the barrow-wight scene:

The Movie-goer's Guide to The Fellowship of the Ring mentions a missing scene in that movie, in which the hobbits lay their hands on rare and powerful weapons in the Barrow-downs east of the Shire. Instead, Aragorn presents them with a selection of swords on Amon Sûl, and never hints that they're anything but ordinary weapons.

This missing scene from The Fellowship of the Ring raises a problem for Merry on the battlefield before Minas Tirith. In the original version, he is armed with an enchanted blade of Westernesse, and uses that weapon to make the Nazgûl vulnerable to Éowyn's own attack. In the movie, though, he finds himself in the same situation with an ordinary sword, so that (in principle) the Witch-king should have survived.

Many readers have suggested that the solution to this question lies in the Extended Edition of The Fellowship of the Ring, where we see Merry presented with an Elvish sword as he leaves Lórien. The idea that he could use this in place of his Barrow-blade from the book does indeed seem quite plausible.

Matters are complicated, though, by a scene in The Return of the King where we see Merry practising with a blunt sword in Dunharrow ('You won't kill many Orcs with that!', jokes Éowyn, and directs him to the armoury to have it sharpened). This is inconclusive, but it sits uneasily with the idea of Merry's weapon being an enchanted gift from Galadriel.

Well and all, the relationship of wraith to elvish material is inconclusive, but so is the relationship of wraith to living human. Merry is sort of bashed around in the witch-king fight, but he's upanattem the very next day; and Eowyn takes much more injury from her broken shield-arm than she does from the arm with which she stabs the witch-king.

I mean, it is hard to have a tender, redemptive moment with a dying relative only moments after both your arms have been rendered helpless, so there were clearly practical reasons for leaving out the gift-with-purchase of killing a ringwraith. I'm not a fan of it, because hello to the halls of healing anticlimax, but I can understand some of the reasoning.

The biggest problem with Una-as-Eowyn would've been Ethan Hawke as Faramir. Now that's a dealbreaker. I've had a hate-on for Hawke since Reality Bites. ::shudder::

I got the impression she was trained for battle, but had never been in one

She'd received training, but if that training had been with the practical purpose of her standing to fight with the army then Eomer wouldn't have been so dismissive of her before the army rode out. Boy, that scene erks me. I can see Eomer being resigned to dying in battle, but Theoden is leaving the entire kingdom in Eowyn's hands, with the probability of bloody last-stand fighting going on, and no one is quibbling at her ability to lead. In the book, I got the impression that she was more than capable of taking her fair place on the walls if need be.

He's wearing her down on purpose, right? Is that because he wanted her stumbling and quaking for the fight, or sort of a larger scope thing, that all the other actors were pretty fatigued after years of filming, and she would've seemed too energetic next to them?

Raquel, I think he was wearing her down on purpose to get her stumbling and quaking. There is a grand tradition among directors who want their actor to look truly ruined and haggard, to just do the scenes over and over again until the actor can barely stand -- the drunk-as-hell, punching-the-mirror scene from Apocalypse Now, a sequence in Dune where David Lynch drove Kyle McLaughlin to actual screaming tears.

I'm pretty sure PJ wanted her to look like she could barely stand, and had decided the best way to do that was to push her until she could barely stand.

(According to Martin Sheen, the drunk-as-hell scene was not an over-and-over type of situation so much as an actual drunk-as-hell scene that went further in improv than planned. He planned to punch at the mirror; he didn't plan to connect and cut himself; having cut himself, they all went with the ensuing psychodrama.)

(Sort of a quibble, though -- Sean's point about some directors liking realism more than the actors do still stands.)

I would have said, generally, that Jackson isn't that sort of director. Based on other comments actors have made, it sounded more like he was a bit of a technician, not caring where the tone of the voice came from so much as how it came out. (After all, he makes actors act against nothing all the time.) But, maybe he mixes up his tricks more than is obvious.

According to Martin Sheen, the drunk-as-hell scene was not an over-and-over type of situation so much as an actual drunk-as-hell scene that went further in improv than planned.

Yeah, that one wasn't so much that they kept going over and over, but that when the scene started going to a VERY intense emotional place, they all went all the way there.

But, maybe he mixes up his tricks more than is obvious.

This, I think. Yeah, I don't see Jackson as one of those directors either. Actually, I'd imagine he only did it for the "physically exhausted" aspect of it, rather than any emotional reality. If, in fact, it wasn't that he just didn't like any of the earlier takes.

Based on other comments actors have made, it sounded more like he was a bit of a technician, not caring where the tone of the voice came from so much as how it came out.

I think you're right--one of the commentaries pointed out that the scene where Sam rescues Frodo in the tower of Cirith Ungol was completely rethought in the editing room, so much so that the two actors were completely surprised when they saw the final cut, since it had a totally different meaning than the way that they filmed it.

From Wizard News:

HOWARD SHORE WINS TWO GRAMMYS FOR RETURN OF THE KING

The Lord of the Rings snagged two Grammys at the pre-show awards tonight, for Best Score and Best Song (Annie Lennox's "Into the West", which also won the Oscar for Best Original Song at last year's awards.