This one was tough- so I though- since people don't float, and because tons of fabric dragging behind you isn't a good idea- that the tails of Belle's dress, can be attached to your finger! Keep the length and cut down on costume frustration. Trying to draw this out as if I were going to make it, so hopefully it helps!
In the original, and in Yuna's Special sphere- there is a very large flower behind them- I thought it might be cute to make a smaller version the same way you would make fairy wings or something and have it on your back, maybe even attached to the corset to exclude shoulder straps. To give you the silhouette of the rose floating behind you (but smaller and doorway friendly)
You could customize a hand mirror to look like the same one from the film and hold it as a prop, for kicks! Instead of having some freaky giant one between your feet like in the original XD