There are a few questions at play here: 1) Does your girlfriend really have hypoglycemia? 2) If yes, then what is the cause of the hypoglycemia? and 3) How does one correct hypoglycemia?
Hypoglycemia, or low blood sugar, is usually the result of an excess amount of insulin in the blood. Persistent hypoglycemia is usually only seen when patients with diabetes take too much insulin or there is an extra source of insulin production within the body (such as a pancreatic tumor). Aside from these situations, the body can usually regulate the level of blood sugar within a normal range through the use of hormones and glycogen (the storage form of glucose) breakdown.
If your girlfriend has been tested on several occasions and found to have a low blood sugar, then she should be evaluated further to determine the cause of her hypoglycemia. This typically starts with measuring the concurrent levels of blood sugar and blood insulin levels. Once the underlying source of the hypoglycemia is identified, then an appropriate treatment strategy can be undertaken. In the meantime, ingestion of carbohydrates (ie, sweets, juices) throughout the day can help raise the blood glucose level if it is in fact on the lower side. It would be advisable for your girlfriend to speak with her primary care doctor
about these concerns.