I'll upload another picture which shows the armour and the shoes.
The feathers made of craft foam. I like this material because it can be transformed by heat. If You'd like to follow my technique here's a mini tutorial below.
First of all cut the drop shaped feathers and then hold each piece above a toaster (or You can use a heat gun too). When the feather gets warm pick on the two edges and pull softly. If You do it right there will appear the main spine on middle of the fake feather. Finally, glue them together and it will be reached a wing form. Keep in mind You should make a right side and a left side wing.
I can't help to love all the details you have put down in this cosplay. Like the feathers, or at least the fabric that is all folded (I think ). I can't image how long time it could have take. And also you make a beutiful Gwendolyn.