Don’t involve your granny - it’s not helping you and it cannot be a sane way to solve the problem. Either your granny will side with you and your mum will go crazy or she ll side with your mum and you ll think that no one loves you. I think it’s important to set boundaries and remind your mum it’s your body your choice. As mentioned before sex toys are safe/disease free and pregnancy risk free and you re mum should value your responsible approach to sex. Tell her that even if it doesn’t make her happy it’s a reality and it’s not by taking away your toy that she ll suppress your sexuality. I ll use this opportunity to discuss contraception as well. To be fired up this way it’s probably that your mum is afraid you ll make the same mistakes she did when she was your age. So maybe you could try to reassure her, may be tell her that your school is okay and it won’t impact it or that it’s a way for you to fight against anxiety related to sex for example. Somehow and unfortunate you ll have to be the adult here. Good luck.