Hard to say it does look like the mid rif part is more notably layered. The dress also doesn't follow the same kind of curvature as the source material and yours currently looks more like a dress. The bottom part of the 'gown' in the source also becomes a little wider at the bottom.
I'm not sewer (i'm trying though), but I would do the white midriff as a shirt underneath, with a dress ath the bottom and the top part at the top and then have a velcro connection for the back between the two (for ease of getting in and out).
I hope that helps.