In 2002, Armstrong joined the cast of medico-legal drama "MDA" on ABC alongside Jason Donovan and Shane Bourne. However, she left the series at the end of its second season. In the series her character, Dr Ella Davis, left the firm that was the focus of the show. After "MDA", Armstrong appeared in films "One Perfect Day", "Oyster Farmer", "Virus", "Car Pool" and . On 10 May 2008 ABC-TV started screening a six-part series "Bed of Roses" with Armstrong in the lead role as Louisa Atherton. In 2008 she appeared in the film "Reservations". In 2010, "Bed of Roses" returned for a second season on the ABC followed by a third and final season in 2011. In the same year she starred in the short film, "The Forgotten Men", alongside Jack Thompson and Gyton Grantley. 2016 sees Armstrong return to Australian screens in the series "The Wrong Girl" for Network Ten.