According to police, Mary Cole, 34, was charged late last week in the May 14 incident.
Officials said Cole told them she knew there was an extra ignition key in the van and said her son often climbs into the vehicle to listen to music.
Police said they found a key in the ignition after the car rolled down the hill and struck another vehicle. The boy rolled out the driver's side door, but suffered no broken bones. He was released from a Pittsburgh hospital on Wednesday.
Previous Story: New Castle boy, 8, jumps out of family minivan before crash