It was a 2 lane road. The posted speed was 45 mph. The other car was going 10 to 15 mph below the posted speed and kept stepping on their brakes. After following them for approx. 1 mile, I decided to pass, I signaled and checked my blind spot and began to pass. Just as I was coming up on the other car they turned on their signal and turned in to me. I had no time to react. My car ended up in the ditch and almost flipped over! There were two cars behind me who weren't paying attention and didn't see anything. There was a witness working on a fence 320 ft away. He said the other car had their blinker on before I started to pass. I think he saw their brake lights going on and off or possibly my blinker. My 19 yr old son was in the car with me, he also saw no blinker on until it was too late. My ins co says I am the majority at fault. I disagree. Can I fight this?