What would happen regarding item claimed by widow and other member of family if nothing written about it?

What my husband did was put a wheelchair lift and hitch on his sister's car bc it wasn't approved for mine. It was put on Sept 26 and he passed Oct 2. It was never used. It was on car with agreement we could use the car as long as we needed. Nothing was said about lift and hitch when he passed. She is now refusing to have lift and hitch removed and returned to me. She agreed on Oct 11 if I paid to remove it she would have it removed. As of Dec 1 she has not done so. The chair is being given to his mom but she has no car and can't drive so he made sure it was understood I was to sell lift. She claims he told her to do what she wanted with it. A couple other issues: she bought a kayak from me on Oct 6 but has not paid for it. I asked for house key back and did not receive and things were missing so I changed locks.