This Seeking Tech guide will explain how you can quickly unlock the Hey, Listen! trophy and achievement.
When you first arrive at the Grand Trad, the game will explain how you can consult Gallica by pressing the Triangle or Y button.
For this trophy and achievement to unlock, you will need to consult Gallica 100 times in total. She does not have to give unique responses, so you can just keep consulting her until you unlock Hey, Listen!