IIRC, “heartless bitch” and “normal teen” are pretty much synonymous. What I considered to be normal teenage behavior, my mom saw as hell on wheels; neither of us has quite yet forgiven each other for our differing viewpoints, and it’s been nearly a decade.
One bit of advice right off: DO grow thicker skin. Your daughter will on purpose say things intended to hurt your feelings, because, let’s face it, you’re raining on what she sees as her parade. If you understand and accept that she is trying to hurt you, and don’t let her, you will be better off. Just remember YOU are the parent and SHE is the child, and insist, insist, insist that she respect you.
I would never have dared to say “Fuck you” to my mother, even over the phone because frankly, I was scared of her. Hell, I wouldn’t say it now, because I’m still scared of her. But that sort of exchange should be forbidden when dealing with a parent, because it is a respect issue. I trust you would never say it to her, either.
You may want to try negotiating. When your daughter gets home, talk about why she needs the tongue/whatever piercing, and why you need her not to have it. And whoever mentioned above that reputable places won’t pierce regardless of consent for those under 18 is right – tell her if she wants it when she’s old enough to have it done herself, then she can do it. See if you can compromise for now and come up with something that is acceptable to you both. Example – maybe if she dyed her hair blue that would be okay (obvious “rebellion” but not injurious to tissues, somewhat embarrassing, and it will grow back eventually). It might be a good idea to include dad in this, too. Discuss with him prior to the moment; you don’t want him to be unprepared to be in the United Parent Front, or worse, to actively take her side.
Another possibly helpful thought: DON’T let her behavior embarrass you. What she chooses to do at this stage in her life is very little if any reflection on her upbringing and very much a reflection of her desire to rebel against it. She is (to a degree) an autonomous person, even though she is a minor and in your care. You can’t control her every move – don’t try to. She will do things that are obnoxious and thoughtless and potentially embarrassing, but only allow her actions to reflect on her. She may discover that when she does something stupid, it makes her look stupid, and you may come off as the supportive and appreciated parent you deserve to be.