Jessie of Team Rocket is unabashedly self-centered and overly confident in her own abilities, but when it comes to Pokémon Contests, her dramatic flair and flamboyant nature make her naturally drawn to the beautiful displays of skill. While she would have difficulty in Hoenn, the birthplace of the Contest, Jessie was able to use each defeat and disguise to grow stronger, making her a forced to be reckoned with when she finally entered the Sinnoh Contests.
Throughout the Hoenn, Kanto and Sinnoh regions, Jessie would don multiple disguises to compete hidden from the Twerps. She would cycle through multiple outfits and names, from Jessica, Jesslana and Jessebella, until finally settling on Jessilina in the Sinnoh region. But, while she was almost never recognized as being from Team Rocket, Jessie, at least to start, was still very prone to her original thieving ways.
She would often cheat in contests, attempting, with or without James and Meowth's help, to rig the results in her favor -- though this never went quite as smoothly as she'd hoped. For example, in season 9, episode 30, "Going for Choke," Jessie teams up with a longtime rival of May's, Harley, to attempt to prevent her from winning the final ribbon needed to enter the Kanto Grand Festival. Not only is Harley's Pokémon unable to win the contest for Jessie, but her disguise is outed as a result of Harley's "assistance."
Until Sinnoh. Having learned from her mistakes in Kanto and Hoenn, Jessie begins to take on a new strategy for her contests: battling fair and square. As Jessilina, Jessie exhibits a style that's completely unique from every other contestant by putting herself into the appeal round, whether it be through allowing James' borrowed Carnivine to chomp down on her head or using Dustox's whirlwind to fly. Not only is this incredibly in-character by making Jessie the star of the show rather than her Pokémon or their moves (though it wouldn't be much of a show without them), it helps to make her performances memorable and interesting, which results in her nearly always advancing to the battle round.
She even begins to win ribbons -- though at first, she believes it to be due to James' and Meowth's help, as per their previous cheating attempts. Understandably, she is overjoyed when they tell her that such was not the case -- she won with her own skills, and as a result, she decides to stop scheming and start training. Like any good Coordinator, Jessie nets wins and losses, but she works to hone her craft and earns each one of her Sinnoh Ribbons through grit, out-of-the-box thinking and sportsmanship.
But, just because she was growing as a Coordinator didn't mean she was above cheating if necessary -- as in season 12, episode 41, "Dressed for Jess Success!" being under the weather is no excuse not to participate in the contest, and she convinces James and Meowth to attend in her place, disguised as Jessilina. Her influence and training have clearly rubbed off on her team, who fight fiercely for their friend and even manage to win the ribbon.
Jessie's passion for Contests, especially once she starts playing fair, brings out the best in her, as she focuses on taking care of her Pokémon, surprisingly friendly rivalries and putting on a show worthy of a Top Coordinator. Unfortunately, her loss at the Sinnoh Grand Festival cuts her promising career short, and she returns to the conniving Team Rocket member we all know and love her as -- but one can't help but wonder what heights she could have reached if she had continued down the Contest Path.