I hope she continues to get away with this. However, wild animals are notoriously unpredictable. That's sort of implied in the word "wild". Most of the time a shark may not be especially hungry. They eat big meals and it takes them a long time to finish digesting and assimilating it. There's also evidence that the Great Whites generally do not think of humans as prey (not enough blubber, maybe, and too much neoprene), and most attacks are due to their mistaking us for something greasier, like a seal.
I hope she has the wisdom and experience to recognize when a shark is hungry and in an indiscriminate mood.