This sounds like me when I was her age. I am 29 now.
It is difficult for busy, and growing(!), teens. I, too, would pass out at the doctors...from blood pricks, allergy testing. From now on, I ask ahead of time if I can lay down while they take blood. It helps.
Encourage her to eat breakfast and to keep snacks in her backpack, purse, and locker. Be careful with the sugar as this can cause an increase in the blood sugar, but then you risk a bigger drop in your blood sugar level once the insulin reacts to it and can make things worse.
I need at least something about every 2 -3 hours. My current fav is Erin Bakker's organic mini-cookies - they have whole grains (take longer to process and break down) and all organic ingrediants. I keep saltines in my car. And crackers and nuts at work.
I would only be concerned about her driving if she has a history of a hypoglemic shock. For now, encourage her to identify early symptoms (ranging from moodiness, nausea, dizziness, sweating, shaking, lack of concentration) so she can become proficient in taking care of herself and knowing when to step away from activities and get some calories in her.
Best of luck!
she might be hypoglycemic which means she needs to try best to avoid foods with lots of carbs and sugar...
also getting a second opinion could never hurt