I do not have any daughters but i have a couple little sisters i know that you probaly dont want to take advice from someone who doesnt have a daughter but you should take advice from a teenager herself. I have a tattoo on my back. also i have some piercings. i have my bellybutton-ears-and my nose pierced. so i think you should allow them to get as many tattoo's as they want. also i think you should trust them to be able to get piercings. and something doesnt happen to every person that gets a piercing. the only way that will happen is if they do not take care of it and/or they do not what they are told to do so it does not get infected.