Berthold began acting on German television in the 1960s, often in TV movies or plays. On stage, she was part of the original 1964 cast of Anatevka, the German title for the musical Fiddler on the Roof. She was heard on German radio in the Paul Cox crime series and as Ellen Macintosh in Raymond Chandler's Pearls Are a Nuisance. In animation, she dubbed the White Queen on Alice in Wonderland and Ketty on Maya the Bee.
She appeared in episodes of the long-running crime dramas Derrick, Der Alte, and Der Kommissar (often as a victim or prostitute). Berthold later began co-authoring books, mostly focusing on military events, and directed documentaries on the same topics.