Erika Coppess doubted her dancing ability, but she became a showstopper. One of 12 women taking adult tap dancing at Ellwood City’s Diamond Dance Academy, Coppess and her classmates took showstopper honors at the recent East Coast Elite competition. At an earlier Access Broadway event, the women took a platinum award and placed second overall. But for the women, who range in age from thirtysomethings to the 53-year-old Coppess, it’s not about the titles and trophies.