I keep coming back to the idea that someone has both paid you a complement and requested your services. Be gracious and say something like "I am really happy you liked what I made. I had such fun doing it. I am sorry about making one for you, but I don't make quilts for sale." That accepts the complement nicely and politely lets the person know that you consider her request a job or commission that you are not willing to accept. It also puts the person on notice that you don't make freebies for your friends either.