What can one do in a situation like this?

I have a friend from NY who hit a lady in her car on the highway…it was my friend’s fault. He asked the lady if they could settle out of insurance and she agreed. All he gave her was his drivers license number, address and cell phone number. She probably has his license plate number. She has no insurance information. My question is, what can she do with the information she has alone if he decides not to follow thru?