Try something like this… With the dress selected on the scene tab, go to the surfaces tab. Select the outer dress material (I don’t have the dress so I can’t speak to what it’s actually called). On the surfaces tab, change the Glossiness to, oh, 65%. Change the specular color to one that makes sense for the color of the material (e.g., if it’s red, a near white red color), change the specular strength to about 40%. Give that a whirl. If the specular response is too wide/big/covering then increase the glossiness percentage. Reduce if it’s too small. If it’s about the right size but it’s too bright, decrease the specular strength. If it’s not bright enough, increase the strength. It’ll take some trial and error but you’ll get there.
A long time ago I wrote up a mini-tutorial on how to adjust poser materials for DAZ Studio, you can find it over on the forum archives here: http://forumarchive.daz3d.com/viewtopic.php?t=156773