If the loan was in your fathers name name only and he died, your mother did not have to keep making repayments! I doubt she will ge the money back now but its worth a try.
Debts should be paid off by the deceased's estate in the order of funeral costs, death taxes, secured debts and unsecured debts. However, where the deceased's estate is not large enough to cover debts, a lender cannot make a claim on the estate.
Lenders are also prevented from claiming from relatives, unless debts were taken out in joint names