It's too bad, my city used to have "bike rodeos" run by volunteers for kids to learn to ride and learn the rules of the road in a non-intimidating area like a large parking lot. That being said when I was 10-12yrs old I rode all over town on my bicycle. We all did and I live in a fairly large city. The best the OP can do is ride with her and make sure she is wearing a helmet and whatever other safety gear if needed. Like other have said, riding behind her in single file and keep an eye out for any hazards would probably be the best idea.