She may overeat toward the end of the day because her spartan breakfast and lunch have contributed to a strong drive to eat. Aim to have fun exercising instead of pushing yourself to burn off calories and redesign your body. Exercise should be for health, fitness, and, in some cases, competition. If you truly need to lose weight, exercise can help by creating a calorie deficit that reduces stored body fat. You can do this by eating a little less, exercising a little more, or combining the two.
Moderation is a better policy.
An exercise physiologist or a certified personal trainer at a local gym can help you develop a personalized exercise program that will focus your workouts on improving your fitness and stamina, not endlessly exercising to pound and punish your body to lose weight. Your training program should include at least 1, if not 2, rest days per week. Your muscles need days off to heal and refuel. Otherwise, you'll feel chronically fatigued and be at risk for injuries. If you fear that rest days mean fitness loss and fat gain, relax.