My father in law and I went out to eat at a restaurant with a very small and tightly spaced parking lot.There is a large sidewalk at the outer side of the parking lot. Clearly marked parellel parking on other side of sidewalk.As we came out of the restaurant, there were no vehicles parked behind my truck ( Nissan Titan). We sat in the parking lot for about 5 minutes talking. I checked all my mirrors and could not see any vehicles behind me. As I said, this parking lot is very tightly spaced and my truck is rather large, therefore, I had to back almost completely straight out. As I was backing, I felt it bump. I pulled forward, we got and only then did we see the tiny little car parked on the sidewalk, only 6 feet from the back of my truck. I went inside, found the owner, and walked outside with her. She seemed to know that she was in the wrong for where she had parked. We exchanged info and both went on our way. I understand that yes, technically, I am at fault as I was the moving vehicle, but had she not been parked illegally and so close, I could have seen her it could have been avoided. What course of action should I take to dispute?