The girl was struck by a vehicle while attempting to board her school bus in Bensalem Township, Pennsylvania on the morning of January 6 when she was hit by a white Ford F-150 pickup truck.
The investigation revealed that Kathleen Wesley, the driver of the pickup truck, failed to stop for the red stop signals on the school bus, police said.
A test of her blood also revealed that she was under the influence at the time of the crash, police said.
The 12-year-old girl was treated for serious injuries and remains in the hospital.
Wesley was arrested Thursday and was charged with aggravated assault while DUI, aggravated assault by vehicle, recklessly endangering another person, meeting or overtaking a school bus and reckless driving.
She was arraigned and sent to the Bucks County Correctional Facility on 10 percent of $100,000 bail.