[2] When Ruah was 5, the family moved back to Portugal,[2] where she attended St Julian's School and, at 16, began acting in telenovelas.

[4] She returned to Portugal where she continued acting, and in 2007 moved to New York City to study at the Lee Strasberg Theatre and Film Institute.

[4] Ruah stated that she grew up in an environment that was both Sephardic and Ashkenazi;[2] her father is of Portuguese-Jewish ancestry, and her mother's Jewish roots are in Russia, Ukraine and Portugal.

[8] Ruah starred as Special Agent Kensi Blye in NCIS: Los Angeles, which first aired on September 22, 2009.

[10] On January 8, 2018, it was confirmed that Ruah would co-host the Eurovision Song Contest 2018 in Lisbon, Portugal alongside Catarina Furtado, Sílvia Alberto and Filomena Cautela.