Depending on the material and where the patch is, you might be able to either darn the patch, sew on an applique or a patch accent, sew a pocket over the frayed patch, redesign the dress (maybe add a flounce to the skirt portion if the frayed part is near the bottom of the dress, or ... just look at what other people are wearing, with your frayed dress in mind, and think about what you might do to your dress to make it resemble the ones you see and like. I'm sure there are many other ways to fix it, if it is fixable. Sometimes there's nothing you can do that won't spoil the line or the style of the dress. In that case, shrug it off and donate it to good will. Good luck!
DYI LiLa, January 2011