Born in Döbeln, Bezirk Leipzig, John competed for the sports club SC DHfK Leipzig during her career. As Sabine Mobius, she won the silver medal in the heptathlon at the 1982 European Championships, behind fellow East German Ramona Neubert. Competing under her first married name of Sabine Paetz, she won the silver medal in the heptathlon at the 1983 World Championships, again behind Neubert.