Investigators said the woman, whose name was not released, was giving the girl a driving lesson in the van Tuesday when the teenager accidentally pressed the accelerator instead of the brake and sent the vehicle crashing through a fence and into Lake Montebello, The Baltimore Sun reported Wednesday.
Police said the girl, her aunt and the aunt's 53-year-old mother escaped the vehicle without injuries.
The aunt is facing charges including knowingly permitting a child under 15 to drive a motor vehicle on a public road, and knowingly permitting a motor vehicle to be driven on a public road by an unlicensed person. She could face a total fine of $430 for the violations.
Police said the state of Maryland forbids anyone from driving on public roads until they are 15 years old and have obtained a learner's permit.