Is the questioner sinful after causing an accident that led to the death of a non-Muslim woman, especially since investigations proved her 100% at fault, and the insurance company paid the blood money?

So long as the incident occurred without fault or negligence on your part, neither blood money (Diyya) nor expiation (Kaffarah) is obligatory for you, and accidental killing incurs no sin. In the event that blood money (Diyya) becomes obligatory, it is sufficient for the insurance company to pay it on your behalf.