Grahn grew up in a working-class family, something she considered to be significant for her work as an actress.

She initially planned to become a writer or journalist but was persuaded by Per Ragnar to seek a theater education at Marieborg Folk High School in Norrköping in 1964.

In 1965 she joined the Marionette Theater in Stockholm, and from 1967 to 1970 she studied at the Scenen School in Malmö.

Osten wrote the role of the movie guard in her debut film Mamma (1982) especially for Grahn.

[3] Grahn also had roles in The Simple-Minded Murderer, Night of the Orangutan, Babels hus, Eva & Adam, Svenska Slut, Goltuppen, Morrhår och ärtor, Rederiet, and Henning Mankell's The Fifth Woman.