You don’t have to do anything, but if you want, you can call her and be like, hey, you seemed upset, can we talk about it? And just hear her out.
At the end of the day, it’s your body and you’re an adult and can make your own choices. And ear piercing is not a big deal imo and she’s being kind of dramatic to get upset about it… but I could see her being hurt that you didn’t talk to her about it. That’s relatable. You could have a chat about that if you want.