It seems to me she's a compulsive eater. Food compulsion is hard to manage without help. She can restrict for a while (and I don't even think she restricts that much, her diet intake is normal diet intake) but soon it gets to a point when you need to eat what you've been denying yourself, and then it's a binge fest for days - hence the quick weight gain. NOT healthy - for the body or the mind. She needs to treat the compulsion first; there is no intuitive eating when you're addicted to food.
Also having to feed a family while being on a diet must be hard. Cooking for everybody, seeing everybody eating cakes, pizza and pasta and having to munch on a salad. Either everybody eats more or less healthily or it takes a lot of constant willpower.