Yes, I was perplexed. There are two possibilities that made the drop correct: 1) the ball last crossed the margin of the hazard at a point adjacent to the right side of the green; keeping that point between herself and the hole, she dropped behind the hazard; 2) there was a ball drop.
Because of camera angles, etc., I would not doubt her drop based on the telecast. I assume there was a rules official right there, and there was plenty of evidence about where the ball last crossed.