If her kids went to public school, perhaps she would push for the school to actually fix the menu to work better for taste while still meeting the guidelines, something that is completely possible and other schools are doing. Who knows? Maybe she would simply send their lunch, an option that is available for the vast majority of schools.
Since when is lunch the only meal that a teenager is going to get during a day? That is the average amount that they were served before the new regulations. What happened to them being responsible for their own food that they want extra? Students don't have to go hungry, especially not in high school. They can bring more food with them from home (none of the guidelines ban this, only individual schools). They can buy extra food a la carte (again, the guidelines do not ban this). Many high school age students can even leave campus to get food.