The student pilot stated that she was practicing touch-and-go takeoffs and landings during her second solo flight. She completed three uneventfully. On the forth one, her approach speed was higher than normal. She landed the airplane and rolled out on the runway. When she attempted to turn onto a taxiway, the airplane was going too fast, and she taxied off of the runway and into a ditch. The outboard 2 feet of the left wing was curved upward, and the right horizontal stabilizer and elevator were bent.