Yeah, this one is tricky. Ideally you'd model it as one single piece in something like Marvelous (and it might be worth paying someone to do it for you, perhaps on DeviantArt, if you really want to replicate it).
This is the closest I could come up with and I don't have a match for the string accessory. I know I've seen something like it but I can't remember what set it is part of.
This is the best I can do and it doesn't have the pleating that your picture does; unfortunately, unless it's designed in, dForce won't do that. This involved a large amount of hackery and messiness and can't be described in a short paragraph so, if it's of interest, let me know and I'll send you the instructions.
May the Force etc..
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