According to the flight instructor, the student pilot was hover taxiing the helicopter along a taxiway that paralleled runway 10, when she asked him to stop, and make a left, 90-degree pedal turn. At the time, winds were from 230 degrees, at 8 knots. The student pilot initiated the pedal turn, and as the helicopter reached the 90-degree position, it began a spin to the left, which increased in velocity. The flight instructor then advised the student pilot that she had the controls; however, the spin would not stop. It became "very fast and I wasn't sure which way we were spinning." The flight instructor then reduced the throttle, but the spin "got faster," so she quickly lowered the collective "to get the helicopter on the ground." The helicopter then landed "hard," the left landing gear impacted the engine exhaust, the tail rotor blades hit the ground and were sheared off, and the tail boom was separated near the transmission. No preaccident mechanical anomalies were noted with the helicopter.