My 14 year old daughter used my iPhone 3 GS for 3 years and took very good care of it. I originally had our home phone number ported over to a cell phone because everyone in our household had a cell and the landline was never used.
She started out only taking the phone with her when she went to a friend's house or stayed after school for sports or chess club. She was very responsible and did not abuse having the cell phone with her. She is mature for her age. (She attends a small private school and has 4 older siblings) I have raised her to appreciate all she has.
She now has the iPhone 5. She understands it is an expensive piece of technology and that she is very fortunate to own one. She is not spoiled. She earns the usage of the phone by doing chores and keeping her grades up and attitude proper.
I also passed down my first gen iPad when I upgraded. She uses it for drawing, writing short stories, homework (as she is able to print wirelessly) as well as watch vides and play games. Technology is a great thing and I think our youth should learn to use it responsibly.
Only you know your child and if she is responsible enough to own one. I read a lot of negativity here on kids having iPhones or iPads and many of these people either do not have kids or are still living in the past. I did not own a cell until I was 26. My older kids ( ages 27, 25, 23 ) got their first cell phone when they started driving. (Those phones were dinosaurs compared to the phones of today), and were pay as you go.
Times have changed and new technology is available and constantly progressing. We have an iMac, 3 Apple TV's and an Air in our house and I want my daughter to be capable of using this wonderful technology, competently. I am not one of those people who say "When I was that age" because when I was that age, things were different. I want to give my kids advantages I did NOT have at that age.