Might be something he noticed with the hand? It looks like it's highlighted when she's waving to him. She waved goodbye to him with her right hand the first time they met.
Great catch. Rukia on Page 16 waves with the left hand while the corrections officer (NOT THE WARDEN! EVERYONE STOP SAYING THAT!) touches her chin with her right hand. In previous chapters (won't link) she uses her right hand for expressiveness. This isn't for sure though because I can't find the corrections officer using her left hand and she uses her right hand here.
you could say that about her ability in general. but i wonder if she'll come across an opponent she couldn't 'overpower' despite her knowledge, it's not like her esp makes her extra strong since so far the first two 'misbuttons' died via poison and the third was already a demented old man strangled with a pillow