Is your wife seeing a endocrinologist or a GP? I was diagnosed by a GP but found a specialist as soon as possible. He had me see a nutritionist, and a lot of food info about carbs and fats etc were discussed but it did take time for me to learn what affected me foodwise. Everyone is different, but some carbs cause spikes in bs levels and some are slower and therefore dont cause extremes in bs levels. Maybe if she would check into the glycemic index it may help in making food selections. Diabetes is a balancing act, and what one diabetic can eat another may find it really causes a spike in bs for them. When your bs is taking a dive you may feel really awful. .. Also making sure to eat small meals through out the day and not just three meals. But the real question is does you wifes doctor know she is having these issues? Is it maybe a possibility her meds need to be reevaluated? This should be mentioned to her doctor if it hasnt been already.
"bad dizziness violent shaking and she almost passes out."
"She just had blood work done and everything was fine"
What did they test? What has the doctor said?
"...result of her sugar coming down quickly"
Sudden spikes and drops in glucose levels can cause drastic changes such as fainting. One has to be not only careful about what they are eating/drinkin, but also monitor and keep track as to not cause this to happen. Proper nutrition, moderate exercise, and weight control are the answers to controlling diabetes.
Since you kept it a secret as to what "get her levels to manageble levels." means, what her preprandial and postprandial levels are, or what your wife and you are doing to control her diabetes, or whether she is at proper weight numbers, no further thoughts can be provided.
In the meantime, please don't let her get behind the wheel of car until this is resolved and she gets her diabetes under control.