Call the Insurance Commissioner's office and make a complaint. Take immediate legal action. The negligent party has to take your car as they find it. The impact made things worse and therefore the insurance company should have to authorize the repairs.
Contact an experienced, wrongful death attorney in your locality. The attorney will investigate the facts and circumstances surrounding the death of your loved one, and he or she will make an intial determination as to who caused the death and what are the potential sources of recovery for the family.