You would first have to check if the auto was covered for bodily injury including partial or permanent disablement caused to other person; and, as I understand that the auto insurance would be required to have this clause in the insurance policy.
Second, you may file for claim in the high court as a writ petition to hear and decide the matter, the lady being old and having spent huge amount in treatment; which would have to be attached in the petition against the insurance company. You would also have to claim the interest, compensation, damages for harassment by the insurance company for using dilatory tactics to dissuade the genuine claim.
thanks.