How can I convince my mom to let me peirce my bellyon?

Well, my mom let me get 2 holes in my ear, and I took really good care of them and I've had them for about 6 years. I'm far from fat, and skinny-ish ( by skinny-ish I mean not anerixic looking but more curvy) anyways, she just wont let me any tips to convince her?