Poly knows the importance of always stretching, be it before fleeing from the angry guards of a megacorp or before taking part in a dance recital! Dancing was fun (typically) and helped keep her limber~!
To be honest, she's probably less stressed when doing it before a heist, though - the worst then that could happen would be she's caught and played with for a few days before getting away. If she messes up at the recital, it'll be in front of all the other cubs and the parents and guardians. She's been here for a while, and she'd like to be here for a while still - the world she's on is relaxing, peaceful, and safe. She'd also like to keep in contact with her guardians for a little bit after she leaves - the last thing she needs is them having embarrassing stories to recite to her each time!
So, while she's stretching and trying to get ready in time to the music, she sees a boy recording her. She may have a bit of a fancy, so her response is just to stick her tongue out at him a little.