When my cats pee where they are not supposed to, I have a spray to conteract the urine and the smell. It is called "Urine Eliminator" by RugDoctor. I have another one: Simple Green Bio Dog which Rids the active stain and odor when he messes up. It worked on the cat messes as well. Try the RugDoctor one first and see if it will eliminate the odor enough so you can finish the quilt and then in the wash it goes. Good luck with your project.
Sharon