Although insulin and blood sugar can affect potassium levels in the blood, the level of potassium in the blood is usually normal after a low blood sugar episode. I would suggest checking the potassium level in the blood when the blood sugar is normal and your child is feeling fine. If it is low, I would consult with a pediatric endocrinologist to look for other causes such as an overactive thyroid or excess amount of the hormone aldosterone, which can also be associated with high blood pressure. The information Dr. Lebinger has given is about the best lay person's explanation I've found. An EEG can rule out an epileptic seizure.
Blood work is in order.
Other than that, all you can do is comfort your child and help them through this very frightening experience. We looked into the possible causes of this incident, and, after mind analyzing it, we can only wager an educated guess that her Ultralente had overlapped, causing too much insulin to be in her system. It's very disturbing to me that endocrinologists don't inform us of this possibility following an extreme low. We need to have knowledge of everything that may effect our children who are living with this disease. That way we can better deal with situations such as this, rather than finding out after the fact, that this can happen.