Sällström made her first stage appearance in Hudiksvall at the age of 15, in A Midsummer Night's Dream. She became famous in Sweden in the 1990s, after portraying the teenage girl Victoria Bärnsten in the soap opera Tre kronor. Thereafter, she appeared in numerous productions, and received a Guldbagge Award for Best Actress in a Leading Role for the 1997 film Under ytan. 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.