OK. I didn't know the part of contests not being mentioned at all. Sure, if it wasn't stated that she ain't changing her goal then she will remain a performer.
I disagree trying contests (or whatever else she went to do in Hoenn) was required to improve whatever aspect of Serena's character and goals. Every time Palermo showed up she was there to belittle Serena. She was good performancer on her own and she clearly did showcases wholeheartedly.
I think Serena wouldn't have thought or considered she needed to improve had Palermo never stepped in. And she really didn't need to because that was part of character development included as well.
Anyway as much as I would like a Coordinator Serena. She's fine as a performer as well. She's good at it.
Contests are mentioned, but the profession of Coordinator is not. She even states in the last scene of the episode that she's "going to experience Contests to improve her Performances", and that her goal remains to be Kalos Queen.
Though on the subject of Palermo, the woman only spoke to her twice pre-XYZ 45; once to tell her she couldn't beat Aria as she was (which she was right as Aria trounced her), and once to tell her to withdraw when her hand was hurt, which led to Serena realizing what Aria has that she doesn't. She never really belittled her but made her question what she was lacking, and once Serena realized that, she offered her an apprenticeship. In fact, Palermo's last lines in the series are "I'm your fan". She really wanted what was best for Serena and it's obvious from early on, and just took a brusque way of going about it.
I think Serena's development line is a bit too misunderstood sometimes, and the Showcases with it, in that they're looked at too much through the frame of "well she aces her Performances so she's good", but Showcases and being Kalos Queen are repeatedly hammered to be about more than your ability to perform well. The crux really came when Aria told Serena that a Queen needs to smile because that smile gives others strength, so when you see the girls in the Master Class crying on stage, despite their performances being good, it says what they lack. Even Serena lacks that ability to give freely until she comes to the realization that she's always received.
Granted, I could write a dissertation on Serena's character, so don't mind me too much, ha ha.