"I would like to compete with my female instructor at Pro Am Competitions as a leader and a follower.

I competed in Bronze in 1999 and 2000 as a leader and did very well, but I am toying with the idea of doing twice as many entries by competing as a follower and a leader.

Can this be done? I am interested in Ohio Star Ball for one of the comps"

Not at a traditional ballroom competition, but there are alternative ones for same-sex partnerships where lead/follow changes are expected. There might perhaps be something in that world which you and your (opposite sex, professional) teacher could fit into, at least its worth researching.