Firstly, this achievement (as of 30/07/14) is still glitched, HOWEVER, I believe there is a way around this!!
As soon as you have your 3rd character, Finn, in your party (who you get on Chapter 4) you can select "Party" during battle and swap out your party members. Do this and swap out Aurora for your inactive character and complete the battle. You then need to start a new battle (this time Aurora will not be in from the start) and win that battle.
Here's the thing.........at this point if your achievement pops, GREAT, stop reading and count your lucky stars!
If you didn't get the glorious "ping" you should have seen in the top right that you completed the criteria for the achievement by getting the Uplay "Action" associated with this achievement. As long as you get that you can be assured you have met the criteria for the achievement.
Next, play on a little until you see the little save symbol in the bottom right, just for OCD's sake
OK, here's the deal! Load up the Xbox One Uplay app and go along to your games, choose Child of Light and navigate to Actions and select "all actions" at the bottom of the screen......................."PING!" the achievement should pop.
So BEFORE you go deleting saves, playing offline, disconnecting from internet etc. Just load up Uplay and GO TO THE CHILD OF LIGHT GAME SECTION AND LOOK AT ALL ACTIONS!