The flight had been vectored for runway 13R by approach control from the point of initial contact. It was then handed off to tower; there was no verbal coordination between approach and tower. A military transport helicopter executed an approach to the same runway ahead of the accident airplane, and terminated at about a 300-ft hover over the runway. The pilot of the accident airplane requested vectors for separation; tower responded separation '...should be just fine....' Shortly thereafter, while the airplane was over the threshold of runway 13R, the pilot requested confirmation that she was supposed to be behind the helicopter. The tower responded '...you were cleared to land on the left runway.' The pilot responded 'Okay understand we were one three right.' As the airplane was flaring, it encountered vortex turbulence from the helicopter and control was lost. The tower never issued the accident airplane a landing clearance to either runway, nor was a clearance to land requested by the pilot.