I really like that you considered practicality in the design of these dresses, since lots of people go too elaborate in their designs and the end result is something really uncomfortable looking. The dresses fit well with both the movie designs and the book description of the nobilitys wear being comfortable, stylish and relatively simple compared to typical wear of nobility elsewhere in the world.
I like that the winter dress has high collar and long sleeves, since lot of people don't seem to consider how cold winters can be, and how it feels when you have exposed skin on cold weather. I also like the way the dress is constructed, with the high necked underdress, the skirt and sleeves possibly belonging to another underdress and then that separate bodice on top of everything. It gives the dress realistic feel, since in the past people wore very layered clothing, and the layers would also add warmth in winter. I also like the blue and silver color scheme, it's simple and pleasant looking, but obviously the wear of somekind of noble lady. I really like the shape of the bodices collar and it's hem, both are pretty inventive, but practical and they look really pretty. The only issue I can see is the slight train the dress has, would drag in the snow and when she goes indoors/warm place the snow would melt and she would have wet skirt, which would freeze stiff if she had to go out doors when it's still wet.
The travel gown looks simple enough that it's believable for a noble lady to actually wear as a travel gown, but still has this elegant style. I also like how it seems like it's somekind of riding gown, since it looks like the dress has a cut out panel on the front that allows the underdress to be tucked up when riding, without showing her legs. The dark bluish-purple color of the dress also makes it seem good color choice for travelling, since mud stains at the hem wouldn't show up badly when she arrives at her destination and possibly needs to make good first impression.
The camp gown looks really great, it has pretty unique cut, but actually looks somewhat medieval, since having one half of a dress in different color was actually extremely fashionable at some points. I like the shape of the collar and how the upper sleeves puff slightly, since they add something really feminine to the look, but it wouldn't look out of place next to Susan and Lucys camp gowns from the movie. This dress just looks like it was custom made and fit for the noble lady, while Susan and Lucy wear ready made dresses that were quickly modified to fit them better, and thus have slightly less fancy ones. The belt looks really nice and while we don't see ones like it in the movies, I could actually imagine something similar to be worn. I also really like the darker and lighter purple used in this dress, they match well and add to the feminine feel of the dress.
The night dress is really pretty and looks like it would be comfortable to sleep in. I think that the only issues with it are, that the sleeves might be too large, since night gowns aren't made to show off a nobles wealth, so they could be more practical. I'm also bit uncertain about the ties at elbows, since those might feel bit too uncomfortable when twisting and turning asleep. While I like the belt, it makes the dress look less like a nightgown and more of a really simple every day dress.
The battle dress looks really pretty and I like how it kind of matches with the armors, and even Susans battle dress from PC (movie versions obviously). I also like how you gave it relatively full skirts, so that she can move pretty freely and wouldn't die because she can't kick, or run fast enough. The issues I have with it are that her throat is revealed and that she doesn't seem to wear any chainmail, so the only parts of her that are actually protected are her chest, stomach and lower arms, which could end pretty badly in an actual fight. Her breast plate probably would slide around since it doesn't have any shoulder straps, and it limits her mobility lot since she probably can't bend or twist her waist at all. LWW movie also doesn't give the characters actual full plate armor, they still wear armors that are mostly chainmail, so the metallic breast plate looks slightly out of place. It's still pretty good design, but it would work better on a queen rallying her troops and wearing "fake" armor, not on a person actually meant to take part in a battle.
I love your design and color choices for the coronation dress. It's relatively simple cut and it's pretty similar to Susans coronation dress, with the buttons down the front and the way the sleeves are constructed, so I can easily believe that she and Susan had their dresses done by the same seamstress and that they perhaps picked the way they would look like together. It makes your oc seem really connected to the canon story, but at the same time the dress isn't just a pink and gold version of Susan coronation gown. I also like that golden stripe at the collar, though it's slightly unclear as to if it's an actual collar or trim.
These designs are really good and inventive, they feel like they really fit the setting, but they aren't just recolors of the canon dresses with only slight modifications. You seem to have in general really good eye for colors and design of medieval-like fantasy dresses, since they are unique but don't appear too modern for the setting.