These kids live in mobile-phone saturated environments, and I'm sure if your DD really *needed* a phone there would be someone with one she could use!

I'm not really a luddite, but I do remember a time (not too long ago) where we all coped fine, planned ahead and thought on our feet - without instant access to telecommunications. However the thing about these young ones is they've never known a world without them, and a lot of social networking happens via mobiles and online. I suspect this is the real reason your DD wants one, so as not to be out of the loop.

*Sigh* this is all ahead of me, all I can suggest is negotiate negotiate negotiate. Perhaps if the issue won't go away, you can make a contract that she has to work towards and the reward (after a suitable amount of time and EFFORT) could be a mobile with a limited plan.