Convince mom to let me use her car?

Ok i sell avon at the encouragement of my mother. Things are going ok but theres one problem. Whenever i need to put out brochures or run avon related errands shes wont allow me to drive unless shes in the car. The issue with this is there are some days more so than not that she says shes "too tired" to go anywhere. Even though all sh has to do is sit in the pengers side and ride. This has been going on for weeks. If she does not feel up to it she wont go er go I cant drive her car. Well this would be fine if i had a car of my own but i dont. She never bought me one bc she said it was "too much freedom" for a woman in her 20s. So now i have to save up to get my own car. Until i can find a full time job the only means of making money I have is avon. Im not trying to be a brat and i know it her car but its not like im wanting to go joy riding its just strictly avon business. How do i convince my mother to allow me to borrow her car for business.