First off, well done! This is a very exciting design with many details thought out. I love the lightness of the costume, your attention to period detail and silhouette, and your sense of playfulness. Truly a great design for an intro class!
A little forewarning, I'm going to be a bit more specific and tough than I usually am in my critiques. Costume design is my profession, and I think you can handle it with the amount of work you have on deviantart. I also think, looking at your other work, that you have reached a stepping stone in your rendering and I'd like to help push you farther *wink*
As I said before, you've paid great attention to silhouette and conventions of the period. You've also been attentive to proportions, which is very helpful in dealing with directors less visually inclined.
If you're going for true proportions of the period (which I doubt you are, but might as well include it), the bodice is too low on her hips. The bodies (bodice) should be at her natural waist, not below. Usually these kinds of oversights happen because we have a modern eye (can't be helped), and upon occasion it's in the audience's favor. I personally like this touch as it brings her look out of historical reenactment and does indeed make her into more of a modern caricature. Be aware that this will make her legs appear shorter and make it MUCH harder for her to sit.
In terms of technique, you have a very solid basis from which to grow. Your color choices are strong, and your sense of faces and hands is great.
I gave you a lower score in this section because I think you have a lot of potential for growth, not because you are unskilled. All of your fabrics appear to be the same weight, and the flatness of the color makes this look to me as if it's all Jo-Ann cotton (cosplay) or that the final product will have the same appearance as a fondant cake.
I'd like to see the heaviness of all that trim weigh on the silk of the dress, the draping of the panniers to have real shadow and highlight in the folds (not soft and round, but more likely stiff and slightly angular). Her hair also carries the same flatness as the clothing, so when I look at only your drawing, I don't know what fabrics you plan to use or how the costume will move. This is very important for a director to be able to imagine! Think chiffon versus dupioni. Marie Antoinette, for example, was absolutely lavish in her choices of fabric and how much yardage she'd lug around on those hips. This means stiff silks, brocades, beaded trim (which is very heavy), gold embroidery...You missed the opportunity to create a caricature that utilized all her extremes.
Overall I think your design is strong and extremely clear! With the bold color choices, it is definitely apparent that she is meant to be a caricature of Marie Antoinette. You have so much potential - My only hope is that you really pay attention to fabric choices and highlight and shadow.
Thank you so much for your critique of my work! I really appreciate your input and all the advice you have given me. It has helped me immensely!