Question regarding Tiger Barb Behavior?

I have a tiger barb tank with six fish in it. Three of these are green tiger barbs. While i know that tiger barbs will rest or sleep in an almost vertical position and will seem to be "shimmying" a bit, one of my green barbs frequently takes this position, and instead of resting, her top fin is totally expanded/open, and her entire body seems to shimmy more fiercely than i've ever seen any of them do.

I was wondering if she could have an air bladder or other issue, and hope that someone can answer. I'd really appreciate any input.

If it might be her air bladder, is there anything i can do?

thank you in advance.