Women man, I am so sorry to hear this. There's a couple old sayings that line up.

"Can't teach an old dog new tricks" I'm just going to assume you're 17, so she's been the boss for 17-18 years and what she's been saying has been going. Children don't have an opinion, and now that you're getting older and almost to the point of legal you are quickly approaching the age where she cannot control you anymore and that's where the "Save it for when you're 18" comes in... It's her last shred. My mom did this too.

"You can lead a horse to water but you can't make them drink" You can try and try and try to be the adult and have a calm conversation and you can do everything right on your end, but that will never dictate her reaction. You still do it though because then it will show your Grandma how you're trying to take this seriously and your mom is acting more emotionally immature than you. Grandma will see it I promise because she already has her eye out for why her daughter acted this way over a vibrator... Be prepared to apologize for your actions too. You're not fully innocent and said a few things you shouldn't have, but be better than your mom and own up to your mistakes.

Good luck and update us!