If for some reason your mother was found to be at fault by both car insurance companies, then her insurer would cover the other driver's damage and she'd need to make a collision claim for her vehicle's damage.Either way, the insurance company that is paying for your mother's damaged car would determine if it were a total loss or not. If the vehicle is unable to be repaired or the cost of repairs is beyond a certain monetary threshold, such as 75 percent of the value of the vehicle, then insurers will total out a vehicle. The total-loss threshold varies depending upon state laws and car insurance company guidelines. If her vehicle is declared a total loss, the insurance company will determine its actual cash value and pay out that amount. If your mother has not yet filed a claim with the other driver's insurance company she should do that now. She should also notify her car insurance carrier about the accident in case claims come in against her policy.