No. She could not have done this accidentally or on purpose. The autopsy would have been able to determine the cause of death as drowning if that were the case. As it stands the autopsy results were inconclusive. Meaning it was impossible for her to have done this accidentally or on purpose. Water in the lungs is the first thing they look for. They can also tell if water entered the lungs while the person was still alive, or if the water entered the lungs after death.