A breakup in which one isn't demonized nor demonstrated as a terrible person? No grand reveal? There wasn't even a hint of drama? It's... nice, right? Like, yeah, she has a thing for baseball players and admires their physique and determination, she's also just a teenager, so she just did what she felt and broke up. She's not a terrible woman, just a teenager going through the motions and finding what she likes.
And he? Yeah, he's looking for something different, too. That's life. It's such a nostalgic send-off, I wonder if the author went through a similar breakup.