The Loop is done while skating backward on the right edge. You sort of wrap yourself up while jumping and time the landing so that you end up again going backward on the right edge. It’s hard to see how she made the mistake since the timing between two and three revolutions is so different. In contrast, the Axel is done while skating forward on the right edge and lands going backward on the right edge, so it requires an additional 1/2 turn.
Here’s what i don’t know or understand- couldn’t she try it again in her program?? Or does she lay out the program to judges beforehand and its one and done per attempts?