Are you sure she's a she? If by "barb" you mean one of the spurs (the claw-like objects on either side of the vent) - it's usually the males who move them back and forth when they're courting a female. Or sometime they'll crawl around their cage alone spurring the substrate. I've not seen females "wagging" their spurs, but I'm sure plenty goes on that we never witness - until someone does notice.