Queensland police say that the schoolgirl gave the two boys - aged 12 and 13 - food which she had laced with a household chemical.
The boys were unharmed after the incident, which took place when the girl was visiting their home in Brisbane.
The girl has been charged with attempted murder and administering poison with intent to harm, and two counts of acts intended to maim.
The police said the chemical - the name of which has not been disclosed - was added to their food on Sunday.
"It was something you would find around the home," a police spokesman said.
"It was reported to police after they realised what they were eating wasn't quite right."
The boys are understood to have told their mum and dad who then contacted the police with the allegation.
The unnamed girl is expected to appear in a children's court later today.