The pilot reported losing thermal activity during the return leg of a cross-country task. On descending to 2000 feet above ground level, she elected to carry out an outlanding and selected a field. The pilot reported experiencing difficulty on maintaining wings level on final approach. The glider apparently struck the ground with the left wingtip during the attempted landing and spun through 180 degrees, sustaining substantial damage. A site inspection of the ground marks and wreckage trail by the club Chief Flying Instructor indicated that the landing had apparently been carried out downwind.