Vegetables, meats, cold-meats they don't have carbs. However in order to adjust properly your levermir, lantus, etc. intake, you should eat nothing at all, and be in the hospital under medical observation since the procedure is really specific on every individual. A word of caution, please don't do it alone with no medical surveillance.
There are many things in life that we have to fast for. None of them require medical surveillance. None.
For what she’s doing, there are only 3 possible outcomes. One is that things go perfectly and her blood sugar stays flat. She’ll test once an hour to monitor, and she will only be taking her basal insulin.
Another outcome is that she’ll go high, which means either she’s not taking enough, or that the enzyme she’s on isn’t lasting as long as it should.
The third is that she goes low. Which means she’s taking too much. The fix for this is as easy as eating food, adjusting the basal dose the next day, and trying again.
Basal testing isn’t forced work. If it fails, okay- eat food, or take more insulin. Then setup the experiment another day and try again.
She’s already taking the drug now, so this is not anything new. She’s only isolated other variables out to see what the basal insulin is doing. The only thing her doctor will want to see is the test data- what did the numbers do.