Hi Ciara -
Sorry to see you weren’t happy with your Mel dress. I made this dress two years ago, and it’s deceptively complex. If you decide to revisit it down the line, here are some things I worked out doing the project:
Fabrics - looks like you picked a pretty lightweight rayon crepe or something similar. Even though it needs to flow, the fabric really needs quite a lot of body to support itself and give you the right lines. I used a dupioni-type fabric (poly blend with the same texture and hand rather than silk) for the shell and lined it in taffeta.
Structure - I also created a muslin inner bodice to the hip line that had some light plastic boning. This ensured that the dress would have the proper structure over the shoulders and support for the bust without having to depend solely on the ties at the waist. Giving the bodice a facing of the shell fabric, backed with muslin (similar to a jacket facing) will also prevent the rippling on the front edges and over the shoulders. The front edges of this dress are cut on the bias of the fabric, so they need to be well structured or they will warp and stretch out of shape.
Lining - It’s very important, not just to make the inside pretty, but also to provide support, structure and to stabilize edges. Linings should be of complimentary weight and stretch to the shell fabrics, and can help make curves, corners and long lines (eg, the sleeves) crisp and clean.
Hope that helps and you should definitely go for this considering your love of the look.

Below is a pic of the one I did.