In Italy, without acting studies, she made her debut in theater at the age of 17, achieving some brief participations, until in 1983 the writer Antonio Skármeta invited her to participate in the making of his film Burning Patience [es] based on the novel Ardiente paciencia, in the leading role of Beatriz González, the young and naive girl seduced by a postman, who, by plagiarizing Pablo Neruda's verses, manages to win his love.

Sussi is a provincial girl who arrived in Santiago, looking for a job, but on each occasion men seek to take advantage of her, however, a roommate, played by Bastián Bodenhöfer, conquers her with his mysteries and games.

Sussi finally becomes a symbol of a government campaign, a stereotype of Chilean women, in the middle of a tour she discovers that she is pregnant and is forced to abort, in the delirium of fever, hallucinates that her lover comes to rescue her.

In 1994, she returns to work with Gonzalo Justiniano, in Amnesia, in the role of Marta, a political prisoner held in a concentration camp in the desert north of Chile.

In recent years, Marcela Osorio has devoted herself to eastern medicine, without neglecting her acting activities, attending the Public Assistance Emergency Hospital (HUAP), formerly the Central Post Office.