She worked as an actress for more than 15 years, before her death in 2007. She was the stepdaughter of Björn Gedda. Sällström made her first stage appearance in Hudiksvall at the age of 15, in A Midsummer Night"s Dream.
Later that same year, unable to cope with her new-found celebrity, she took a break from filming and moved to Copenhagen, where she worked in a café.
In 2000, Sällström returned to Sweden to continue her acting career. She did not enjoy the success of previous years until, in 2005, she played the role of detective constable Linda Wallander in the first season of the Swedish television series Wallander.
Sällström"s last role was in an Ystad theatre production of Anton Chekhov"s play The Seagull, which she left prematurely due to illness. Sällström was found dead in her Malmö home, from an overdose of sleeping pills, shortly before midnight on 13 February 2007.
She had recently been released from a psychiatric unit where she had been receiving treatment for depression.
Her lifelong struggle with depression was exacerbated by her harrowing experience in Thailand. In a 2006 interview with the editor of the magazine Tove, she said, "I always thought I would be dead by the age of 30."
Henning Mankell"s grief and guilt over her death prevented him from writing the last two novels of his projected Linda Wallander trilogy.