Simple, she did not kill off most of the probiotics living in her gut before she started the high Sugar diet. Probiotics do eat various kinds of sugars, and as long as the probiotics are numerous enough, and have prevented candida from growing too much to begin with, the sudden high Sugar diet will not cause candida overgrowth necessarily.
People who killed off most of their probiotics fare far worse when they eat a high Sugar diet, as the candida yeast already have the upper hand (because the probiotics in their guts are too low in number).