I do think that the OP's daughter is probably too young to have her belly button pierced but blimey, there are some over reactive replies on this thread.
I had mine done over 20 years ago, in my late 20s. It didn't hurt, didn't bleed, it didn't get infected and it healed within a couple of weeks.
The only warnings I would give are have a bar put in rather than a ring. A ring can catch on clothing, buttons etc and increase the risk of puling/tearing.
If you get pregnant take your belly button jewellery out as soon as you know. Don't do what my colleague did and go to A&E for it removing after it started to get a 'bit tight'. She was given very short shrift, quite rightly.
And it's very odd but when you get your period the piercing can become very sore and tender. I've no idea why. It was on my information sheet and it did happen. Not anymore though, being a menopausal lady. However, a teen needs to be aware of this.
And to be honest, much better a belly button piercing than a tattoo of dolphins round the belly button which was very fashionable in the 1990s. After you've had a baby the piercing will still be OK. The dolphin tattoo not so much....