As for her being too young... frankly, yes. Can she pay for the calls herself? Then fine. If not, I would vote, "no".
I do not understand the obsession with having "their own phone", "their own computer". These are expensive, luxurious applicances that a kid cannot afford on their own. How about keeping a "family" Trac or other pay-as-you-go phone, and you dole it out to a child when they are going on a field trip, or a sleep-over, or some other event where a phone might be handy? There is no need for her to have her own.
I do not subscribe to that "It's a different world" mantra. I think we are far too obsessed with insisting that we be connected to each other at a moment's notice at the touch of a button every single moment of the day. Ask yourself, how did we live 10, 20, 30 years ago without cellphones? We couldn't call each other. We couldn't reach each other. Fire and brimstone did not fall from the sky.
I gladly exchange the inconvenience for a life where we do not have to be constantly in touch.
Well, sorry if it sounds like a rant. But this whole idea of kids having to be connected to mommy and daddy every second with a cellphone just because "what if something happens?" is nuts. Yes, what if something happens? It's a big bad dangerous world out there. It always has been. Better for parents and their kids to learn to live with that now, and not just keep expecting to reach for the cellphone when danger strikes. That's like driving like an idiot on ice and then counting on 4-wheel-drive to bail you out.