Your prosumer camera has to compress light into something like 7 or 8 f/stops from pure black to pure white. To maintain detail in the dress you will most likely have to stop down more than you'd like for her face and the faces around her.
One trick is to soak the dress in tea to achieve an off-white. Or dye it. An off white will photograph as white.
It doesn't matter whether or not your are shooting color. The black to white values remain essentially the same.
If you were shooting with the Alexa with its 13-14 stop range from pure black to pure white, you would be fine. Film too is fine.
Tea-dying is the usual procedure. I did it with some white shirts on a film noir short ( ) and noticed that one wash seemed to remove the tea stain. I'd expected it to stay, and was going to label the shirt for future shoots. You might ask a good laundry, or your mother, about that. Whites have always been a problem, film as well as video, and the tea-dying trick goes way back.
If you can't tech-down the dress your only other choices are (1) to have a grip chase her around with a double net, leaving light on her face but taking it off (most of) the dress; or (2) just keep the lighting ratios such that the dress doesn't blow out. Since you're doing noir maybe you can make the crushed shadows work for you.
A common mistake is to look at two different-colored items with the same luma value and think they will have different contrast in B&W. If you look at some rare color photography on B&W movie sets, you will see colors used on clothing and sets in combinations that would make you question the sanity of the costumers and set decorators... when the tough guy private eye is wearing a pink shirt, for example... but this is a business not of what IS but what Appears to be. So though the colors look "wrong" in color, in B&W they read very well, because their luminance value and tonal qualities have the appropriate contrast.
When you are "faking" B&W from color footage, you have to think about these things or your footage will look stangely washed-out and lacking contrast. You will blame the lighting, but really it was your choce of colors. Try looking at these things on-set thru a dark ND filter, or some daylight correction gel; it may help reveal where you need to make a change. I always double-check my graphics using a monochrome setting on my monitor, to make stuff readable for the color-blind, but also when you do it right for color-blind people, it makes the graphics more effectively "pop" for regular-vision people.
Zone VI studios used to sell a mounted Wratten 90 filter that was meant to judge relative values for b&w film. I had one for years, but it disappeared with a stolen camera bag some time ago. This will probably be difficult to replace.... eBay maybe.
In the "Web of Lies" film noir referenced above I should have shot a Macbeth Color Checker on each set, as a reference that I could have then made against a Macbeth chart shot on Tri-X. IMaking that b&w film reference is still something I need to do - I intended to do at least one more b&w - just need to get up the gumption to set up for processing film again.
The Red camera's raw format is perfect for doing the conversion from color to accurate b&w; there is plenty of room to move values around.
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