Career
In 1991, former East German swimming coach Michael Regner claimed that in the 1980s he had been instructed to distribute anabolic steroids to team swimmers, including Hörner. Hörner came to prominence when she set a world record in the 200 m breaststroke of 2:28.33 at Leipzig in qualifying for the East German team for the 1985 European Championships. There she stumbled, swimming outside her best to place third in the 200 m event.
She also claimed silver behind teammate Sylvia Gerasch in the 100 m event.
Despite winning neither event, she was named as the European Swimmer of the Year. At the 1986 World Championships in Madrid, Hörner, set a world record in the 200 m breaststroke on her way to gold, reclaiming the record from Gerasch who had broken it earlier in the year.
At the 1988 Summer Olympics in Seoul, Hörner, set a world record in the 200 m breaststroke on her way to gold, reclaiming the record from Allison Higson of Canada who had broken it earlier in the year. She was well outside her world record in the 100 m breaststroke, finishing with the bronze medal.