I wanna kill the allstate skank

I have a 98 Dodge Dakota that I did a REALLY nice paint job on 3 years ago. 2 years ago, the daughter of the lady across the street backed into it while it was parked in the street. I wasn't even across from her driveway. The damage really wasn't that bad. I got an estimate for $3200 and her insurance company said they would only pay me $2700 and they were going to take the truck. I said the KBB value was $3900 and NADA was $4200, and they said the value was only $2700. They said they HAD THEIR OWN BOOKS based on average vehicle sales , and they did not have to show me their information. Turns out that is legal with most state’s Insurance regulation departments. I finally fought them for $3200 plus I kept it. It was a weird company I had never heard of. Bottom line is that they have their own books and they can get away with that???