Ellie's first cookbook is fairly clean, so I'd expect her next one to be so as well. She's definitely less stringent than Tosca. She believes that while the majority of your emphasis should be on minimally processed, whole, natural foods, she also refuses to demonize food and believes that eating foods we'd all consider "unclean" once in a while isn't the end of the world--they just shouldn't make up the bulk of your eating.
She classifies food in these categories:
(1) Always: natural, minimally processed, low-fat, low-sodium (these should make up the majority of your daily meals)
(2) Sometimes: more processed but still nutritional (have these no more than 3 servings of these a day)
(3) Rarely: highly processed and not much nutrition (have these no more than 3 servings a week)
For me, thinking of food in these buckets helps me be less obsessed about food and minimizes the emotions I attach to food. I know it's not healthy to feel guilty about eating certain foods, but I still do sometimes. I have to remind myself of Ellie's philosophy and keep in mind that we'll have millions of meals in our lifetime and that eating a few of the "rarely" foods here and there isn't going to substantially damage my health.