Following Monday night's public vote, Ms Cook blitzed her rivals to guarantee herself a spot on the Idol roster for at least a few more weeks.
Idol Host Andrew G announced the result of the public vote before last night's second semi-final.
Up against fellow Idol wannabes Hayley Warner, Seth Drury, Jamila Ioane, Toby Moulton and Stan Walker, Ms Cook's rousing rendition of the Loggins and Messina classic Your Mama Don't Dance struck a chord with judges and viewers.
Judge Jay Dee Springbett tipped her to be star if she stayed true to who she was as an artist, while Marcia Hines and Ian 'Dicko' Dickson also gave her flowing reviews.
Ms Cook has been a sensation on Australian Idol after first wowing viewers in the audition round with a self-written song dedicated to her dead mother.
She was the first contestant to make the final 24 and now is the first contestant to make the top 12.
Via her Facebook fan page run by her older sister, Kate said she was humbled by the support she has received from the Australian public.
"Thank you to everybody for their well wishes and support," Ms Cook said.
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