You might look into lowering her overall carbohydrate intake, not just the sugar and candy.
I've been cycling vigorously for nearly an hour every day for the last 2 years and actually gained more weight. Until 3 months ago - when I went on a low-carb diet. With that simple change, I've lost more than 30 pounds. I don't restrict calories and eat whenever I'm hungry - I've just gotten rid of all the things like bread, potatoes, rice, etc.
What motivated me for this was a talk about the hormones around appetite and fat regulation. Insulin is the hormone that regulates fat. The more insulin, the more your fat cells store energy. The macronutrient that causes a rise in insulin is carbohydrates. On top of that ghrellin is one of the hormones that regulates how hungry you feel. Insulin suppresses the it, so you feel less full and hungrier.
I've changed my diet to be "low carb/high fat", and it's working great and I feel great. We've been sold a lie over the last 30 years that "fat is bad, fat makes you fat" - It's my belief that all the carbohydrates that replace the fat in "low fat" food is what's making so many of us fat.
So looking at the typical food your wife is eating, try dropping the toast, and the sandwiches, and even those Pepsis (and the potatoes, rice, and pasta that are probably staples of your "reasonable dinner"). Replace them with things like cheese, green veggies, meats, and a little fresh fruit. If she's hungry, it's fine to snack - just not on carb-based foods, so again, cheeses, nuts, veggies, etc.
It's mostly the fats in the foods that help you feel full and not want to eat. And frankly, that's the key. Our strongest instinct is to eat because if we don't, we die. We only only have a limited amount of will-power (read thes studies by Daniel Kahneman). Traditional "eat less" dieting is about trying to exert your limited will against an unlimited instinct to survive - and that's why people lose that fight. In the complex system that is the human metabolism, the key is to find the leverage points and manipulate them - and in this case, it's the hormones. "Don't be hungry" was some advice I read. So eat things that get you feeling full.
I'm not following a specific diet plan other than "as few carbs as possible, especially processed ones - and eat whenever I'm hungry". But you could look to the Southbeach diet as an example of a low-carb diet that might be helpful for you.