Her husband Craig Sadler confirmed the news via Facebook late Saturday.
"The love of my life Nikki Sadler suffered an aneurysm on Wednesday. She would already be gone, but she's an organ donor and has been kept on life support to make that possible," Sadler shared. "That shouldn't be a surprise to us. Even [in] the end, she is still giving. She was so loved that I know thousands of you will be grieving with us. There are only a few hours left for me to hold her hand and kiss her forehead."
McKibbin placed third in the reality competition series' debut season following winner Kelly Clarkson and runner-up Justin Guarini. The Texas native wowed judges Simon Cowell, Paula Abdul, and Randy Jackson during her audition with her rendition of Whitney Houston's hit "One Moment in Time." Her performance earned McKibbin the ultimate compliment from Cowell before she was sent off to Hollywood for the next level, "Unlike a lot of other people that we've seen, I would remember you."
Before finding her spot in the spotlight on American Idol, she competed on the first season of the WB's Popstars in 2001 that led to the creation of pop girl group Eden's Crush. Though she didn't make it into the final lineup, she was determined to find her place in the music industry.
Her first studio album Unleashed was released in 2007, followed by the EP Psychotrip in 2012 as part of the group Love Stricken Demise.
McKibbin appeared in various other reality shows following American Idol including three in 2005: a "reality TV stars" episode of Fear Factor, the sports competition show Battle of the Network Reality Stars, and a lead role in E! Entertainment's Kill Reality.
Three years later, she joined the cast of Celebrity Rehab with Dr. Drew during the show's sophomore season where she sought treatment for alcohol and cocaine addiction. She revealed in the premiere episode her struggles trace back to the emotional, physical, and sexual abused she experienced as a child. The loss of her mother from addiction also weighed heavily on her shoulders. Her success led in rehab led to her appearance on the spinoff series Sober House.
McKibbin returned to Celebrity Rehab during the show's fifth season to celebrate three years of sobriety.
She returned to American Idol in 2014 to support her son Tristen Cole Langley not as a competitor herself. Although he was also invited to Hollywood, he didn't make it to the live television competition. On a segment of the show, Langley shared his love for his biggest musical inspiration — his mom.
"My biggest musical inspiration is my mom," Langley said. "Of course, because she's my mom and she's a great singer. She's always been pushing me to do it, now really pushing me, but saying, 'Follow your dreams. Just do what you can do because if I did it you can do it.' She's just an amazing singer. She got third in the first season and I just thought that was awesome that I could do it too."