British close relatives immigrants

You might as well not mention that you have cousins. Just sign up for an American tour. In the eyes of visa officers, cousins are weak. As an unmarried woman, the visa officer can't be suspicious.

It's good that you have collected enough information to prove that your family constraints are sufficient. The visa officer asks you what you want to do in America. You tell him that you are 40 years old, want to go out and have never been to America. Give him a detailed travel plan so that he won't be suspicious.