"You are going to wear this dress, maybe."
Translation:Tu vas porter cette robe peut-être.
Because the English version put it at the end. While it means the same, the Duo system requires manual addition of sentences where word order is changed, especially if not necessary. With time, these things will get added, but it will slow down your Duolingo experience because they're not currently accepted.
I got this wrong because I think I'm confusing something from my days in French class years ago. Is there a construction that goes along the lines of "ce robe ci" for "this dress (here)" and "ce robe lá" for "that dress (there)"?
It would be cette robe-ci and cette robe-là. Not really used in an isolated context, but for distinguishing two or more elements that are necessary to be distinguished. In most cases, cette robe is more than enough.