Sayuri

Assunta is a character of the day who appeared in Friends to the End.

She battled Ritchie in the first Full Battle of the Indigo Plateau Conference. After a fierce battle, both Trainers ended up with only one Pokémon left. Using her Ivysaur, Assunta was able to overpower Ritchie's Pikachu, Sparky, and win the match, much to the shock of Ash and his friends. With this win she advanced to the semifinals.

It is unknown what happened to Assunta after this point, but the silhouette of the second-place League winner at the end of the episode greatly resembles her, indicating that she might have made it to the final battle but lost.

(Source: Bulbapedia)