Is it normal to be 0% body fat for a tween girl?

It is neither normal nor possible. Anything less that 10 percent body fat is extremely dangerous. What is even more dangerous are the drugs people use trying to remove all of the fat from their body. There have been a number of deaths for people trying it.

Your target should be a body mass index (BMI) number within the normal range for someone your height. If you do a Google search for "BMI" there are many calculators available to view your BMI.