I wasn't allowed until I was 13 though my mum has never had hers pierced and never really wears any jewellery save her wedding ring saying that.
Even when I was at university I didn't dare tell her I'd had my nose pierced until after I'd had it done, same with my bellybutton some years later, she wasn't impressed!
I think she needs to realise the importance of keeping them clean and making sure they heal properly.
As said above, get them done somewhere properly, supervised and with decent quality earrings. Make sure she understands how to deal with them during sports etc...
I have to say, I'd probably wait until she was older and wait until something like a special birthday or get her to earn it by proving she is responsible etc...