[3] While living in Paris, Westergren received a call from Swedish director Göran Gentele, who offered her a role in his 1951 comedy film Leva på 'Hoppet'.

[3] She accepted the offer to appear in the film, which also starred a number of other relatively unknown actors at the time, including Ingrid Thulin, Per Oscarsson, Gunvor Pontén, and Jarl Kulle.

[3] The film sparked her interest in acting, and when she decided to study again she sent in applications to both the fashion university college Beckmans designhögskola and the Royal Dramatic Training Academy.

[2] After graduating, Westergren was offered a job at Alléteatern (English: The Avenue Theater) by actor and director Sture Lagerwall.

[3] After Alléteatern she proceeded to work at Vasateatern, where she earned big success in 1956 with Vad vet mamma om kärlek?

[1] While working at these two places, Westergren also played roles at the following private theaters in Stockholm: Intiman, Maxim, Södra Teatern, Folkan, Chinateatern, and Oscarsteatern.

[4] Her comedic roles in the films Fröken Chic (1959) and Lille Fridolf blir morfar (1957) are among her most appreciated works.

She played a controlling wife in the television series Goda grannar (1987) and a dramatic secretary in the soap opera Rederiet (1994–1995).

[1] In the 2000s, Westergren has toured Sweden with her show Mitt teaterliv (English: My theater life), in which she talks about her career and her famous parents.