I would say let her. If she doesn't experience it for herself, then how will she find parts of herself? In the future she may say to herself, "Wow, I can't believe I did that, I learned my lesson". or " Hey, that was fun! I found parts of my 'wild-self' ". If she wants to be wild, guide her to what's good and the consequences of being bad, she might/will learn. Here's a tip: don't be too strict, like a nun, or too loose, like a hippie. Be a mixture, in the middle. Don't take sides. It will only make things worse. I experienced it for myself, when I was little my mother was loose on my sister and she turned out not being aware of reality and she ended up being a horrible person in the future. I now know my limits from that experience.When she turns 18 she's on her own. But while she's in your house, set some limits a lip piercing is close to the border, not the borderline, the border. Sex is on the border ans that's where you step up and throw down. Piercings and tattoos are eh, so-so. Alcohol, sex, etc. is not. They scar physically and emotionally. Let her express her body. I think body art is expressing her feelings and colors of herself, but let her know that they can't be there on parts of the body that can be seen if she wants to get a good or excellent job. Just to let you know, children make mistakes, don't let it happen to them again by guiding them to the right path. Some some piercings are able to be hidden. Lip piercings and tongue piercings are able to be hidden, I don't know about nose or eyebrow piercings. REMEMBER: when she is 18, she is on her own. But while she is under your roof, Set some limits. Hey, boyfriends are 2-5 steps ahead than piercings. I would go with the piercings. That's my opinion. Go with your opinion, not anyone else. It's your kid, it came out of you, you're responsible for her, don't let anyone else tell you how to raise her, if you're not a full 100% about it don't go with it. Here's a tip:How you express yourself in front of her or teach her, that's how she will end up later in life. if you're strict, that will go nowhere If your loose, same thing, some teens with different personalities or ways to live will sometimes teach themselves about the real world and the rewards and consequences. Some, you have to help them.
Thank you for your time.