Nuggets tend to be high in fat and calories, but frozen food is not unhealthy per se. If she wants to avoid weight gain, just avoid both high fat and high sugar foods. Grilled or oven cooked meat and fish, rather than fried, vegetables served without butter or alternative. No oil-based dressings on salads. Fresh fruit rather than high-sugar desserts, [frozen fruit is also healthy, but if serving tinned fruit check it is in natural fruit juice and not a sugar-based syrup].Fruit also in place of candy. For children her age,it is seldom a good idea to say an absolute no to biscuits, cakes, candies etc,but to strictly ration them.