^They could mean she comes off cold and or cocky? Not that she's a problem child the way I'm presuming you're thinking.

They're 12ish(?) They're gonna be bratty. /shrug
I see Kanon as the weird hyper active one, Riho the calm idgaf whatever one, Erina awkward shy one, and Mizuki as the stoic, mature,
flawless goddess one.