The long navy-blue reference has a shaped front edge without visible shoulder straps. Many small pale points trace its closer outline. A quieter glossy-looking fabric area crosses the upper body diagonally and hangs further down at one side. A front opening reveals a larger leg area, with part of a pale ankle strap visible below. The head is cropped at the top. The hands sit lower beside, or partly behind, the body.
This closer hip line makes a clear contrasting reference to the early fullness of the pink ball gown. A long outer outline alone does not mean the same skirt width. The quieter side section does not establish a detachable construction either. This photograph confirms neither a particular glossy fabric nor the internal structure of the upper edge.
For a similar offered dress, inspect the side area from front and back before deciding how much outer volume you want. Try an ordinary step with your intended shoes. Keep questions about that longer section separate from the front leg opening: the image shows both areas, but does not demonstrate their handling or any alternative configuration.