Serena was the only pokegirl whose social development was tied to Ash and honestly, there's nothing wrong with admiring the person you love.Isn't she friendly with Ash at this point? I mean she's addressed him plenty of times, had convos with him and is now going on adventures with him and Goh quite a lot. Honestly I'm glad she's just treats Ash like a normal person. They aren't best friends, she doesn't admire him and she for the most part just respects him. Having a character who's social development is not hugely based on Ash is refreshing especially after having an entire friend group who thought he was superman. Chloe still behaves indifferent towards Yamper and Goh despite knowing them for years so I assume that's just her personality.