According to her mother, when O'Day was four, she was at a performance of The Nutcracker and started to cry.
Her mother asked her what was wrong and O'Day replied, "I'm sad that I'm sitting here and not up on stage." O'Day recalls that moment as the one in which she "officially" realized her love for entertainment. She later majored in political science and drama and graduated with a degree in political science from University of California, Irvine, and is a member of the Alpha Chi Omega sorority.
Additionally, O'Day was featured on the Donnie Wahlberg single "I Got It." On the April 23, 2009, finale of Making the Band, O'Day revealed that she would have her own reality television show for which she would be filming in the spring of 2010.
Before being fired, O'Day received a significant amount of criticism for her conduct while competing on the show, being described as "narcissistic, self-centered, evil, and vicious" by the media and viewers of the show, and as "transparent" by Trump's judges.
The band became known as Danity Kane, and their first album debuted on August 22, 2006, at #1 on the Billboard 200 charts.