The film follows the real-life crimes of Michael Peterson who was convicted in 2003 of pushing his wife down the stairs. In 2008, Armstrong starred the independent romance film Around June.
The series was an instant success and premiered on September 26, 2007 to 10.44 million viewers. Her character has been noted to have many similarities to real-life heiress Paris Hilton.
Samaire has since appeared in notable small roles in films such as Would I Lie To You? In 2006, Armstrong co-starred alongside Lindsay Lohan in the film Just My Luck portraying the role of Maggie, Lohan's character's best friend. producer Mc G offered the leading female protagonist role in the horror film Stay Alive.
The film was a box office bomb and was negatively received by critics. She portrays the role of Abigail, an aspiring photographer and love interest to Jon Foster's character. Despite a worldwide gross of just ,105,095 it was considered a box office success compared to the film's modest million budget.
In September 2013, she played the mother of the blond boy who perpetrated the school shooting in the Sons of Anarchy season six premiere "Straw".
Armstrong made her film debut portraying the role of Kara Fratelli, one of the conjoined twins in the parody film Not Another Teen Movie in 2001.
In March 2008 Armstrong announced she would not return for the series second season as a series regular.