Two 16-year-old girls have now been charged as adults in an alleged plot to kill classmates at suburban Mountain Vista High School in Douglas County.
Prosecutors said Thursday that Brooke Higgins researched places where teens could buy guns and wrote in a journal that she wished she could have been part of the 1999 Columbine High School attack.
Her defense attorney argued against the charges and said she has been treated for depression. Bond was set at $1 million.
Higgins and Sienna Johnson were arrested Dec. 12 after police were alerted via a text-a-tip program.
Prosecutors accuse Johnson of buying a BB gun and mapping plans for the attack. Her lawyer says the allegations have been exaggerated.
Higgins' attorney wants the case to be tried in juvenile court.