Hmmm. I thought I remembered it being pretty consistent within the shooting games, but Marisa definitely pulls off some air maneuverability without the broom in the fighting games. Of course, the game is balanced around everyone being able to do that stuff, so it'd be a problem if she couldn't.
(Which isn't to say she never flies on her broom in those; in particular she leaps on it and tries to ram the opponent on a regular basis in Immaterial and Missing Power.)