I would never withhold a snack. If the student has an elevated bs & wants a snack, they simply the high blood sugar & carbs by entering it into the pump. What kind of snack does the student have? I've found snacks that are high in protein (peanut butter, soy butter, or chocolate milk) are nice, stabalizing snacks.
Your care plan should give parameters for PE & when to exclude (with too high or too low of a blood sugar, or if (+) ketones.
I would not have student bolus for every low reading, especially if they are in checking frequently. You might end up with hypoglycemia instead.
Take a deep breath. Relax. Talk to the student's mom & her diabetic educator/ or the physician's nurse. Priority #1 for me would be to get the orders/ parameters you need clarified ASAP!
Hope your tomorrow is better. Hugs to you.