Although, to be fair and objective these ladies have not done a test where these items are put in stomach acids. If it were i would assume it would get to look like the 3 months normal potato slices in a matter of hours and not months.
I agree fast food is bad for you but to be honest what this woman is doing is using shock examples deliberately to sell her books, and the whole everyone has a "vice" thing is silly because anyone eating any type of Sugar ever under her guise could count it as a "vice" even so far as to say high Sugar fruits.
I believe its just a marketing strategy to be honest, although i do agree that there are more healthy choices then fast foods.