I think the clothing n the figure has little meaning or impact on the actual image, with the figure being so small in the actual composition of the image. It has absolute no impact on the rest of the image so really i don’t see any point in testing any cloth on her besides doing some design shapes or testing a few values. I am no expert in image making or anything like that, but I think you should concentrate more on the actual composition around the figure, and emphasis more detail, and design the shapes around what is happening in the foreground middle and background etc. At the moment there is no separation between any parts of the image. Then you can start to make a focal point with the contrast of values etc. Is the focal point the lady in the image? Even if she is, i really dont think you need to worry about doing some transparent cloth test on her, and she is so small in the actual image. she could just be a a shape design with value contrasts in her if you want agasint the background design.
Like I said i am no expert and just trying to give my input on my limited knowledge.