"But why did Serena win when she did the SAME performance in Dendemille Town? Should’t she have done something different?”
She DID do something different, Pokeani Fandom. If you had paid attention rather than just guessed at things based on their appearances, you would have known that.
While she still uses Flamethrower, Dark Pulse, and Stone Edge, it’s because she’s using Braixen and Pancham. You don’t expect her to teach her Pokémon entirely different sets of moves between each Showcase, do you? And she even adds in Arm Thrust and Fire Blast, which she hasn’t used before.
And the dancing. The dancing inspired by Eevee. The Dancing Eevee taught them. Eevee’s Dancing.
The entire point of those cartwheels and that jump was because that’s how Eevee dances, with lots of spins and jumps
And Eevee’s first reaction?
“OH SHIT THOSE ARE MY DANCE MOVES!”
As the performance continues, Serena, Braixen, and Pancham
Serena wasn’t just in sync and coordinated with her Pokémon on stage Her heart was in sync with Eevee’s as well. She totally understands it’s feelings and wants to share it’s dancing with the world, and this was the first way she could: by allowing Eevee to teach them how to dance and performing on stage.