How they come out probably depends on what kind of parasite she had...
But yeah, the general theory on here has always been that parasites die without food and by fasting you are starving them. Fasting/Juices doesn't require digesting, you absorb all the nutrients instantly..leaving nothing for the parasites to feed on.
I actually had a Science teacher in Jr High talk about humans getting "tape worms" and how in the old days they would put Sugar on the end of the person's tongue and the huge worms would crawl up to get the sugar.