TAKE her to the store to buy the fabric, backing, batting, and thread, and let HER pay for it all. I promise this is the only way to educate and count on your friends to understand what they are asking you to do. Then let her take you to lunch as a partial payment for doing all the work. (The rest of the payment can come when she takes you to lunch again when you give her the quilt -- at the restaurant!)
Jan in VA