Ngozi Okonjo-Iweala relishes a good fight. Which is just as well. Since Nigeria’s president persuaded her to sort out the country’s infamously chaotic finances and rein in its notorious corruption, she’s been hailed by world leaders and reviled by her fellow countrymen.”When I became finance minister they called me Okonjo-Wahala — or Trouble Woman,” chuckles the 51-year-old.