During her studies, she met Helene Schjerfbeck, who remained a close friend for the rest of their lives.

Westermarck and Schjerfbeck were a part of a group of female artists, "the painter sisters."

[5] Westermarck worked for long periods in France, often in the company of Schjerfbeck, and developed a sensible realistic style especially with portraits and figure compositions.

[7] Westermarck also made a significant contribution as a researcher through her cultural and historical works.

She also wrote about women who were pioneers in their respective fields, including Elisabeth Blomqvist (1916–17), Adelaide Ehrnrooth (1928), and Rosina Heikel (1930).