State Farm Insurance?

So, my brother and sister-in-law were selling their truck and I decided to buy it but, since I am only 18 no one would finance it for me so I paid them 1000 down and I pay the truck payment and insurance every mont. Since it is financed it has to have full coverage so they added me to their insurace policy. My question is since it has full coverage can my mother drive it even though she isnt on the insurace policy?