1) Only one with a major outfit design, her teammates are still wearing practical clothing.
2) she’s 12
3) It doesn’t fit previous young female characters that were designed by Kishimoto (Ino, Sakura, Hinata… the only female characters that were sexualized in the manga were older woman) It sticks out like a sore thumb.
4) It’s impractical, it looks more like an outfit she’d wear on a day off than during a mission
5) There’s literally not a single good reason for the outfit change, especially because none of the other kids had major outfit changes