Discipline Katherine. Whether its horse riding, body building, modelling or powerlifting, bodyweight goals are all reached the same way, discipline.
Nina reduced from 62kg to 58kg to compete at the Nationals. She did it with a severly restricted diet, supplements and KB cardio sessions. She simply ate 5 tiny meals a day, drank zero calories and performed plenty of heavy cardio sessions. She needed to maintain her strength as well, which made training tricky, but not impossible. She made 8 of 9 lifts on the day, so she was succesful.
Maintaining an unatural bodyweight is trickier, and not much fun. Nina is attempting to get to 56kg now, she is mad.
Good luck Katherine.