I'm not sure what this quilt is being used for? So I would talk to the person this quilt belongs to, are you doing this as a favor, getting paid, just helping out???? If it's a favor or your just helping out - just let the owner know what the problem is and suggest that they come over and see the problem first hand, that way they will see what goes into the work and they will never make this mistake again. And they can help solve the problem. You could use a serger to finish the edges, pick a color to help it look like binding. If your being paid, and you are unable to talk to this person about adding another boarder and batting. Good luck