If your daughter is concerned about eating breakfast because she is afraid of her weight, then you need to explain to her that when she sleeps, her body slows itself down, especially her metabolism. One of the reasons breakfast is so important is because it starts your metabolism back up. The act of chewing and digesting raises your metabolism rate which is why most people are hungrier at lunch when they eat breakfast than when they skip it. Perhaps something a little healthier than a poptart would be more appealing? (I'm not trying to preach, and I myself am also overweight but that's why I've done so much research on food). Also if the issue is about her fearing being overweight, there is an awsome web sight called CalorieKing.com where she can look up the caloric value of any food, from fruits and breads to her favorite restraunts.
Also, another important reason for eating breakfast is for her brain. If she values getting good grades, this approach may be helpful. The brain needs carbs to function, and after waking up it is especially important to get her brain functioning at top notch with some carbs.
Without any additional information on what she says is her "reason" for not eating, that is about all the advice I can give. I wish you both the best of luck!
P.S. Recent studies show that a high percentage of people who are overweight and diabetic, then lose the extra weight also lose the diabetes. The study was conducted with diabetic patients who had gastric bypass. And now I think I am preaching so I stop now.