The accused, Billie Davis, 56, told cops that she targeted the student for her race.
She told the police that the 18-year-old student "would be one less person to blow up our country."
The victim was standing and waiting for the exit doors to open on a Bloomington Transit bus when another passenger began striking her in the head, the police said in a release.
There was no interaction between the two women prior to the attack.
On Thursday, the police re-interviewed the accused who admitted to using a folding knife in the racially-charged attack and charged her with attempted murder.
It's unclear if she will also be charged with a hate crime.