Not important or relatable but i need some help

So i am turning 16 very soon and i know no one really cares about this stuff and it has nothing to do with this app BUT....... I’m getting a car soon and it’s coming from my grandma. She is giving it to me and told me that i would have to give my mom rides to work when she needed bc she is getting a job soon and can’t drive her car. I am paying for insurance and gas myself which is going to my grandmas bank account. Situations like these with my mom usually go her way no matter what. I get it shes my mom. But she doesn’t pay for anything for me bc i got a job and my boyfriend drives me EVERYWHERE so she doesn’t. I’m getting another job soon and don’t know how to get to drive myself and sister to school, go to work, drive to my mascot duties, and be involved in class that takes a lot of commitment and volunteering of my time. It would be on if she wouldn’t take MY car that I pay for and drive it everywhere. Idk what to do?? She never leaves the house but if shes getting a job she needs the car but shes not being responsible and paying off her car and paying for insurance it instead she’s taking the car that i pay for... any advice???