Jim Verraros, who "went to Hollywood" with McKibbin on "AI," tweeted, "Rest peacefully, my beautiful@nikkimckibbin. You'll be in my heart always. #RestInPeace."
McKibbin, who distinguished herself from the pack with her fire engine-red hair and edgy fashion choices, auditioned for "American Idol" with Whitney Houston's "One Moment in Time," Gloria Gaynor's "I Will Survive," and "Unchained Melody" by the Righteous Brothers. On the series, she covered Bonnie Tyler, Michael Jackson, Pat Benatar, Ella Fitzgerald, Janis Joplin, Alanis Morissette, Melissa Etheridge, Stevie Nicks, Naked Eyes, and, perhaps most memorably, "Black Velvet" by Alannah Myles.
She ultimately lost to Kelly Clarkson, and was one spot behind Justin Guarini.
Her debut album, "Unleashed," was released in 2007, and she released nine singles from that and various other projects.
McKibbin appeared on Dr. Drew's "Celebrity Rehab" (2008) in an effort to conquer substance-abuse issues, and continued her work on the spin-off series "Sober House" (2009). A staple of reality TV, she had previously appeared on "Popstars" (2001), and popped up on "Fear Factor" (2005), "Battle of the Network Reality Stars" (2005), and "Kill Reality" (2005), the latter of which documented the making of the horror movie "The Scorned" (2005), her only acting role.
She is survived by her husband of 13 years, Craig Sadler, and her son Tristan Langley, who auditioned for "American Idol" in 2014.