i personally think it's part of what makes Miyabi, Miki and Haruka awesome.
but they've got different brands.. Miyabi is school-friend bitchy (the type that you go along with and think is funny, but sometimes go "was that really necessary?"), i get the feeling that she's not just trying to be funny for the camera, sometimes it's just fun to mess with people and i feel like she discovered this long ago.
Miki is like the lone voice of sanity in a fantasy world (no sugar coating and no exaggerating either, just saying it like it is). i love that even though she's an idol she recognizes some things as ridiculous, it makes the whole situation more genuine. x3
Haruka is more like the runt who nobody takes seriously until they realize she's the smartest/most talented among them and confident to boot, so she ends up being the one that they all turn to. i personally don't see her as bossy, i think she's just in control which is unusual for someone her age/so new. it's just natural that she would end up telling people what to do, because she's hanging with a bunch of new girls who are looking for someone to guide them. for example, she only seems to help Haruna and Masaki.. Masaki clearly needs someone to help her through, and while Haruna has more confidence personality-wise, her actual performance still needs work and she's still a little jittery. Ayumi is on-point and doesn't get as nervous as the others, and i haven't seen Haruka tell/have to tell her to do anything which i think reflects that she's taking the lead, not being randomly bossy. i also see her as a perfectionist, which i can relate to.