My nephew and his wife asked his mom (my sister) if I would make them a king size quilt. I said I would but they would have to pay for the the materials and to have it long armed. After telling her what they could expect in the cost, which I wasn't even going to charge them for my time, I haven't heard a word from them. Your cousin might back away once she hears what it might cost. Of course, if you really don't want to do it, you just have to say so.