She started with theater work at the age of nine in the play Kalas i Lönneberga at Dramaten in Stockholm. When she was nineteen she moved to New York and studied theater at the Neighborhood Playhouse School of the Theatre for one year. After she returned home to Sweden, she started working at Teater Galeasen in Stockholm with the company Darling Desperados, founded by Ulrika Malmgren. She graduated from Teaterhögskolan i Malmö in 2006.

Wärmländer has worked mostly in television and film. She played in the television mini-series Skuggornas hus (1996) where she played the character Tina. She has also played in shows such as Cleo, Skilda världar and Spung. She acted in the Helena Bergström film Se upp för dårarna, and also Hipphipp!, Itzhaks julevangelium and the Martin Beck film Okänd avsändare.