The Schaumburg girl was sentenced to 15 years in prison, but will spend about 5 years in a juvenile detention facility if she stays out of trouble until she turns 21.
The teen pleaded guilty to attempted murder in connection with the March 2010 beating of a 58-year-old neighbor. Prosecutors say robbery was the motive when the teen attacked the man with a hammer.
The victim was in a coma, lost an eye and underwent multiple surgeries to his brain and skull.