Oh can't wait to see your Ariel!
Yeah there are times when it's appropriate to be upset when someone "steals" your own design. I would not be happy about a direct knock off of say my Queen of the Night costume but another take on the concept of Queen of the Night - bring it on! To claim "dibbs" on something you can't in anyway claim the copyright on (like a Disney Princess in any of their variations) is just silly. As you say - recreations and reproductions are really fair game.