The main thing I considered when making this decision was do I have faith in my daughter. By this I mean do I give her the responsibility to drive on our roads. Can she handle the car, has she undertaken driving lessons and passed her driving test. If she has then she is as much capable to drive as I am. She will lack experience but didn't we all. And you don't become a good driver by reading books, you have to practice.
If a child doesn't show respect to you or to other drivers and doesn't want to learn to drive correctly through approved driving classes then maybe they aren't quite grown up enough just yet. As a parent you know your child and it can be difficult to assess when the time is right. Go by your gut instinct, not just about whether they can drive or not, but are they turning into a young adult in other areas of their life, are they acting responsible at school/college? are they dating? and still seeking out your advice? Sometimes you have to give them a chance to shine and sometimes they still can surprise you. Good luck.