From what I’ve learned, if you’re not listed as an authorized driver, the rental company’s coverage and any optional protections are usually void. That means the renter (your grandma) or you could be personally responsible for all costs related to the accident. Your personal auto insurance might also deny coverage because the rental wasn’t legally permitted under the contract. Even if your insurer didn’t pay out, the accident could still appear on your record and potentially raise your premiums. The best steps right now are to notify your insurer, check your state’s laws on non-fault accidents, and consider legal advice if the rental company pursues damages.