Asking my mom

So I'm 15 and I really want a vibrator. I'm pretty sure my mom knows I do it but I'm not really "getting off" anymore...My mom is pretty chill about stuff like that,I mean she let me get a small tattoo and let me get my belly button pierced.The only thing is she has texted some of my ex's and told them to keep me a virgin,and I still am.How do I ask her?Please I really need help!!